Process for manufacturing white pigment containing products

ABSTRACT

A process is described for manufacturing white pigment containing products. The white pigment containing products are obtained from at least one white pigment and impurities containing material via froth flotation.

CROSS-REFERENCE TO PRIOR APPLICATIONS

This application is a National Stage of PCT/EP2017/053182, filed Feb.13, 2017, and designating the United States (published on Aug. 24, 2017,as WO 2017/140630 A1), which claims priority under 35 U.S.C. § 119 toEuropean Patent Application No. 16156003.2, filed Feb. 16, 2016, andunder 35 U.S.C. § 120 to Provisional Application No. 62/298,485, filedFeb. 23, 2016, each hereby expressly incorporated by reference in itsentirety and each assigned to the assignee hereof.

The present invention relates to a process for manufacturing whitepigment containing products and, more particularly, relates to the fieldof technologies implemented in order to separate white pigments andimpurities by froth flotation for the manufacture of white pigmentcontaining products.

Pigments are generally known as materials that change the colour ofreflected or transmitted light as the result of wavelength-selectiveabsorption. This physical process differs from fluorescence,phosphorescence, and other forms of luminescence, in which a materialemits light. Pigments are used for colouring e.g. paint, ink, plastic,fabric, cosmetics, food and other materials. Most pigments used are drycolourants, usually ground into a fine powder.

White pigments take a special position in the field of pigments due totheir industrial relevance. For example, in the paper industry in Europemore than 10 million tonnes per year of white pigments are used. Whitepigments are also used in paints and coatings. Especially whenmanufacturing dispersion paints, white pigments are the base colour inthe tinting system.

Naturally occurring white pigments are usually obtained by mining.However, generally, such white pigments contain impurities which inducediscolouration such as, for example, greyness or yellowness.Furthermore, these impurities may affect the properties of the whitepigments and, thus, lead to significant disadvantages in their use. Ahigh amount of impurities such as, for example, silicates within thewhite pigments might increase the abrasive properties. Therefore, theimpurities and the white pigments have to be separated from one anotherto obtain a white pigment containing product that is not, or merelymarginally, contaminated with impurities.

It is known in the prior art to separate impurities from white mineralsby physico-chemical separation. The physico-chemical separation processinvolves firstly grounding the metamorphic or sedimentary rock and thensubjecting the resulting white pigment and impurities containingmaterial to conventional froth flotation in an aqueous environment.Conventional froth flotation is a highly versatile method known in theprior art for physico-chemical separating of particles based ondifferences in the ability of gas bubbles to adhere selectively tospecific surfaces in an aqueous suspension containing the white pigmentand impurities containing material. The white pigments with attached airbubbles are then carried to the surface and are removed, while theimpurities that remain completely wetted stay in the liquid phase.

As set out above, the basis of conventional froth flotation is thedifference in the wettability of the white pigments and the impurities.White pigments can either be naturally hydrophobic, but in general thehydrophobicity is induced by chemical treatments. Chemical treatments torender a surface hydrophobic are essentially methods for coating aparticle surface with a layer of suitable compounds.

However, conventional flotation has a significant disadvantage: Asmentioned before, chemical treatments as collector agents are used torender the surface of the white pigments hydrophobic to separate theseparticles by gas bubbling. These collector agents are adsorbed on thesurface of the white pigments and, therefore, modify the properties ofthe pigments. However, this modification may be undesirable in thefollowing use of the white pigments in paper, plastics, paint, coatings,concrete, cement, cosmetic, water treatment, food, pharma, ink and/oragriculture applications, wherein preferably the white pigmentcontaining product is used in a wet end process of a paper machine, incigarette paper, board, and/or coating applications, or as a support forrotogravure and/or offset and/or ink jet printing and/or continuous inkjet printing and/or flexography and/or electrophotography and/ordecoration surfaces. Furthermore, the direct flotation of the desiredwhite pigments is disadvantageous due to quality and economical reasons.

Alternatively, one may consider to use reverse/indirect froth flotationto separate the white pigments and the impurities. In contrast toconventional flotation, in which the desirable white pigments aredirectly floated and collected from the produced froth, reverse(indirect) flotation aims to have the undesirable impuritiespreferentially floated and removed, leaving behind a suspension that hasbeen concentrated in respect to the desirable white pigments. Alsoduring reverse flotation collector agents are used that render theimpurities hydrophobic.

Corresponding methods that use collector agents in reverse frothflotation are already known, one class of collector agents areesterquats.

U.S. Pat. No. 3,990,966 refers to a wet process for purifying calciteore by grinding and forming a slurry of calcite ore, separating saidimpurities from the calcite slurry by flotation of the impuritiestherefrom in the presence of a flotation agent, classifying theresultant calcite slurry, settling the classified calcite in a thickenerand drying the product. As flotation agent a cationic surfactantselected from the group consisting of (a) 1-hydroxyethyl-2-heptadecenylglyoxalidine, (b) 1-hydroxyethyl-2-alkylimidazolines and (c) saltderivatives of said imidazoline, wherein the alkyl portion of theimidazoline is the alkyl portion of a fatty acid of such length thatsaid surfactant is liquid as used.

CA 1 187 212 relates to a process for purifying a carbonate orecontaining silicates by flotation, wherein the ore is subjected togrinding to a fineness sufficient to release the impurities. Thecollector is a cationic reactant selected from the group consisting ofthe following quaternary amines: a) dimethyl dialkyl with 8 to 16 carbonatoms in the alkyl radicals, said alkyl radicals being saturated orunsaturated aliphatic, normal or branched; b) dimethyl alkyl benzyl with10 to 22 carbon atoms in the radical alkyl which is a normal aliphatic;c) bis-imidazoline containing 12 to 18 carbon atoms in the alkylradicals which are normally saturated or unsaturated aliphatic; d) saltsderived from quatemary amines a), b) and c).

WO 2008/084391 A1 refers to a process for purification of calciumcarbonate-comprising minerals comprising at least one flotation step,characterized in that this step implements at least one quaternaryimidazoline methosulphate compound as collector agent.

WO 2008/089906 A1 relates to a process for the flotation ofnon-sulphidic minerals or ores, in which crushed crude minerals or oresare mixed with water and a collector to form a suspension. Air isintroduced into the suspension in the presence of a reagent system and afloated foam containing said non-sulphidic mineral or ores formedtherein along with a flotation residue comprising the gangue, whereinthe improvement comprises using as the collector polymeric esterquats,obtainable by reacting alkanolamines with a mixture of monocarboxylicacids and dicarboxylic acids and quaternising the resulting esters inknown manner, optionally after alkoxylation.

WO 2011/147855 A2 refers to the use of a polymeric quaternary esterproduct as a collector in a froth flotation process, to a method forfroth flotation utilizing the polymeric quaternary ester, to thepolymeric quaternary ester as such, and to methods for the production ofthe polymeric quaternary ester.

WO2010/051895 A1 relates to the use of a composition of A) at least onequaternary ammonia compound comprising at least one organic radicalbonded to the ammonia nitrogen atom and optionally comprisingheteroatoms and having 1 to 36 carbon atoms, and B) at least one aminealkoxylate ester of formula (1) or a salt thereof, where A, B are,independently of each other, a C2- through C5-alkylene radical R1, a C8-through C24-alkyl radical or alkenyl radical R2, R3, R4 independent ofeach other, H, or a C8- through C24-acyl radical, with the stipulationthat at least one of the radicals R2, R3 or R4 stands for a C8- throughC24-acyl radical, and x, y, z, independently of each other, stand for awhole number from 0 through 50, with the stipulation that x+y+z is awhole number from 1 through 100, in quantities of 10 through 5,000g/tonne of ore as a collector in silicate flotation.

EP 2 659 028 A1 relates to the use of a product obtainable by thereaction of a fatty acid, or mixture of acids, having the formula R1COOH(I); and a dicarboxylic acid or a derivative thereof having the formula(IIa) or (IIb) with an alkoxylated fatty amine having the formula (III)or a partial or wholly quaternised derivative thereof; optionally saidreaction between the fatty acid, the dicarboxylic acid and thealkoxylated fatty amine is being followed by a further reaction stepwherein part or all of the nitrogen atoms are quaternised by reactionwith an alkylating agent R5X; as a corrosion inhibitor for metalsurfaces.

U.S. Pat. No. 5,720,873 refers to a method of cleaning calcium carbonateore containing silicate impurities, in which a froth-flotation processis performed in the presence of a specific cationic collector.

AU 2167883 A relates to froth flotation of sized coal effected in anaqueous medium containing a fuel oil collector and a conditionercomprising a product formed by condensing 1 mole of an alkanolamine (I)with ≥0.8 mol of a fatty acid or fatty acid ester, or an acid derivativeof such a product.

WO 00/62937 A1 refers to a froth flotation process in which silicatesare separated from an iron ore in the presence of a collector containinga specific quaternary ammonium compound. This collector has a highselectivity to concentrate silicates in the froth product, while a highyield of iron minerals is maintained in the bottom concentrate orconcentrates.

WO 97/26995 A1 relates to the use of so-called quaternary esters as anaid for flotation of non-sulfidic minerals.

U.S. Pat. No. 4,995,965 refers to a process for purifying calciumcarbonate ore by the removal of silicate impurities from the ore byreverse flotation. The process achieves high yields and low acidinsoluble content of the calcium carbonate product by employing specificcollectors.

CN 101337204 A relates to bi-quaternary ammonium compounds in silicatemineral flotation, and a specific collector which applies a specificbi-quaternary ammonium compound in bauxite or ironstone reverseflotation desiliconization.

CN 101816981 A refers to a specific environmentally-friendly aminecationic collector and a using method thereof.

EP 1 584 674 A1 relates to an esterquat concentrate suitable forproduction of fabric softeners at lower temperatures comprising a) anesterquat compound; b) an organic solvent; c) water; d) a pH modifier.

EP 1 806 392 A1 refers to aqueous compositions containing a specificesterquat or mixtures of specific esterquats.

EP 1 876 224 A1 relates to a stable, homogenous and viscous softenerformulation which contains less than 50% by weight of a specificesterquat compound.

US 2005/0189113 A1 refers to acidic treatment fluids that comprise anacid fluid and an ester-containing quaternary ammonium compound(“esterquat”) and methods of their use.

EP 2 700 680 A1 relates to a process for manufacturing white pigmentcontaining products. The white pigment containing products are obtainedfrom at least one white pigment and impurities containing material viafroth flotation using a specific collector agent.

U.S. Pat. No. 4,606,916 refers to specific quaternary oxalkylatedpolyesters prepared from oxalkylated fatty amines by polycondensationwith a dicarboxylic acid and subsequent reaction with an alkylene oxideand a carboxylic acid or a mineral acid or with a quaternizing agentsuch as methyl chloride, are described. The compounds are suitable foruse as cosmetic active compounds, in particular for cosmetic care of thehair.

EP 0 035 263 A2 relates to specific textile softeners which arepolyesters containing tertiary amino groups or salts thereof with lowercarboxylic acids, for example acetic acid or glycolic acid, and mineralacids.

However, the prior art methods for manufacturing products by reversefroth flotation have numerous disadvantages. The use of such collectoragents is very expensive. Additionally, many of the known collectoragents cause uncontrolled foaming in the reverse froth flotationprocess. Furthermore, many of the reverse froth flotation processes arelimited in that they are selective, i.e. a significant part of thedesired product is floated together with the impurities. Also a greatnumber of the collector agents used so far is considered to be aquaticand environmental toxic. A further disadvantage of the known collectoragent is that they decompose under flotation conditions and therewithloose efficiency.

Therefore, there is a need for an improved method for producing whitepigments by flotation, which method avoids or reduces the problemsdescribed above in relation to the known methods. Such improved methodfor manufacturing white pigments from a white pigment and impuritiescontaining material should especially be an easy to handle andecological method. Also the effectiveness should be satisfactory.

At least some of the foregoing objects have been solved by the presentinvention.

According to one aspect of the present invention a process formanufacturing white pigment containing products is provided,characterised in that said process comprises the following steps:

-   -   a) providing at least one white pigment and impurities        containing material;    -   b) providing at least one collector agent selected from the        group consisting of compounds of formula (1)

-   -   R′ is selected from the group consisting of        -   i) a direct bond,        -   ii) a C₁-C₂₀, linear or branched, saturated or unsaturated            hydrocarbon chain optionally substituted by one or more —OH            group(s), one or more methyl and/or methylene groups, a            cycloalkylene group, a cycloalkenylene group and/or an            arylene group, preferably            -   A) an alkylene radical having from 1 to 20, more                preferably from 1 to 10 carbon atoms, most preferably a                substituted alkylene radical, wherein said substituted                alkylene radical is substituted by 1 or 2 —OH groups, 1                or 2 methyl and/or methylene groups, a cycloalkylene                group, a cycloalkenylene group and/or an arylene group,                or            -   B) an alkenylene radical having from 1 to 20, preferably                from 1 to 10 carbon atoms, more preferably a substituted                alkenylene radical, wherein said substituted alkenylene                radical is substituted by 1 or 2 —OH groups, 1 or 2                methyl and/or methylene groups, a cycloalkylene group, a                cycloalkenylene group and/or an arylene group;    -   R² is selected from the group consisting of a hydrocarbyl group        having from 8 to 24 carbon atoms or a group of formula        R⁴—O-(A′O)_(w)-T-, wherein;        -   R⁴ represents a hydrocarbyl group having from 8 to 24 carbon            atoms; w is a number within the range from 0 to 20;        -   A′O is an alkyleneoxy group having from 2 to 4 carbon atoms;            and        -   T represents an alkylene group having from 1 to 6 carbon            atoms;    -   R³ is selected from the group consisting of a hydrocarbyl group        or a benzyl group;    -   AO represents an alkyleneoxy group having from 2 to 4 carbon        atoms;    -   X represents an anion derived from an alkylating agent R³X;    -   x is a number within the range from 1 to 20;    -   p is a number within the range from 1 to 15;    -   t is 0 or 1;    -   y is 0 or 1; and    -   G represents a group of formula (2);

-   -   wherein;    -   B represents an alkyl group having from 1 to 4 carbon atoms or        represents a benzyl group;    -   s is 1, 2 or 3;    -   R³, X and t are as defined above;    -   N⁺ is connected to R² in formula (1); and    -   (CH₂)_(s) is connected to the quaternary nitrogen atom in        formula (1);    -   c) mixing said white pigment and impurities containing material        of step a) and said collector agent of step b) in an aqueous        environment to form an aqueous suspension;    -   d) passing gas through the suspension formed in step c);    -   e) recovering the white pigment containing product by removing        the white pigment bearing phase from the aqueous suspension        obtained after step d).

The inventors surprisingly found that the process for manufacturingwhite pigment containing products from at least one white pigment andimpurities containing material and at least one collector agentaccording to formula (1)

is advantageous because the aforementioned collector agents effectivelybind much more effective to the surface of the impurities than to thesurface of the white pigments. Moreover, the collector agents accordingto the present invention show a high stability and do not decompose incritical amounts under flotation conditions.

Therefore, the inventive flotation process is very effective incomparison with known prior art processes. Furthermore, the inventiveflotation process is very ecological since the used collector agents areless toxic in comparison with known prior art collector agents. Thewhite pigment containing products obtained from the inventive processshow good brightness and have a low yellow index.

A second aspect of the present invention relates to the use of the whitepigment bearing phase obtained by the inventive process in paper,plastics, paint, coatings, concrete, cement, cosmetic, water treatment,food, pharma, ink and/or agriculture applications. The white pigmentcontaining product is preferably used in a wet end process of a papermachine, in cigarette paper, board, and/or coating applications, or as asupport for rotogravure and/or offset and/or ink jet printing and/orcontinuous ink jet printing and/or flexography and/or electrophotographyand/or decoration surfaces.

Advantageous embodiments of the present invention are defined in thecorresponding sub-claims.

According to one embodiment, the process involves an indirect flotationstep leading to the formation of a froth containing the impurities and awhite pigment bearing phase with the white pigment containing product.

According to another embodiment, the white pigment is a white mineralpigment, preferably selected from the group consisting of naturalcalcium carbonate or ground calcium carbonate, calciumcarbonate-comprising mineral material, dolomite, barite, aluminiumoxide, titanium dioxide and mixtures of the foregoing.

According to another embodiment, the white mineral pigment is analkaline earth metal carbonate, preferably a calcium carbonate and mostpreferably ground calcium carbonate (GCC).

According to another embodiment, the white pigment containing materialcomprises impurities selected from the group consisting of ironsulphides, iron oxides, graphite, silicates and mixtures thereof. Thesilicate may be selected from the group consisting of quartz, a mica, anamphibolite, a feldspar, a clay mineral and mixtures thereof andpreferably is quartz.

According to another embodiment, the silicate is a white colouredsilicate selected from the group consisting of wollastonite, kaolin,kaolinitic clay, calcined kaolinitic clay, montmorillonite, talc,diatomaceous earth, sepiolite and mixtures thereof.

According to another embodiment, the amount of white pigment in thewhite pigment and impurities containing material of step a) is from 0.1to 99.9 wt.-%, based on the dry weight, preferably from 30 to 99.7wt.-%, more preferably from 60 to 99.3 wt.-% and most preferably from 80to 99 wt.-%, based on the dry weight.

According to another embodiment, the ratio of white pigment:impuritiesin the white pigment and impurities containing material of step a) isfrom 0.1:99.9 to 99.9:0.1, based on the dry weight, preferably from30:70 to 99.7:0.3, more preferably from 60:40 to 99.3:0.7, and mostpreferably from 80:20 to 99:1, based on the dry weight.

According to another embodiment, the white pigment and impuritiescontaining material of step a) has a weight median grain diameter in therange of from 1 to 1,000 μm, preferably of from 3 to 700 μm, morepreferably of from 5 to 500 μm and most preferably of from 10 to 80 μmor from 100 to 400 μm.

According to still another embodiment, the compound of formula (1) ischaracterized as follows:

-   -   R¹ represents an alkylene radical having from 2 to 6 carbon        atoms, more preferably 4 carbon atoms;    -   R² represents a hydrocarbyl group having from 12 to 24 carbon        atoms or a group of formula R⁴—O-(A′O)_(w)-T-; wherein        -   R⁴ represents a hydrocarbyl group having from 12 to 24            carbon atoms;        -   w is a number ranging from 0 to 10, preferably from 0 to 3;        -   A′O represents an alkyleneoxy group having from 2 to 4            carbon atoms; and        -   T represents an alkylene group having from 1 to 4 carbon            atoms, preferably having from 2 to 3 carbon atoms;    -   R³ represents an alkyl group having from 1 to 4 carbon atoms;    -   X represents halogen, sulphate or carbonate;    -   AO represents an alkyleneoxy group having from 2 to 4 carbon        atoms, preferably having 2 carbon atoms;    -   x is a number within the range from 1 to 10; more preferably        within the range from 1 to 6; and    -   p is a number within the range from 1 to 10, preferably within        the range from 1 to 5.

According to another embodiment the compound as provided in step b) isselected from the group consisting of compounds of formula (1a):

wherein,

AO, p, t, x R¹, R², R³ and X are as defined in the first embodiment,preferably as defined in the previous embodiment.

According to still another embodiment the compound of formula (1a) ischaracterized as follows:

R¹ represents an alkylene radical having from 1 to 20, preferably from 1to 10 carbon atoms, preferably having form 2 to 6 carbon atoms and morepreferably having 4 carbon atoms;

R² represents a hydrocarbyl group having from 8 to 24 carbon atoms,preferably having from 12 to 24 carbon atoms;

R³ represents a hydrocarbyl group having from 1 to 4 carbon atoms,preferably an alkyl group having 1 or 2 carbon atoms and more preferablyis a methyl group;

AO is an alkyleneoxy group, preferably an ethoxy group;

X is an anion derived from an alkylating agent R³X; preferably chlorideor sulphate;

x is a number within the range from 1 to 15, preferably within the rangefrom 2 to 10 and more preferably within the range from 1 to 6;

p is a number within the range from 1 to 15; and

t is 0 or 1, preferably 1.

According to another embodiment, the compound of formula (1a) possessesat least one of the following characteristics:

R¹ is derived from a dicarboxylic acid, a dicarboxylic acid chloride, adiester of a dicarboxylic acid, an anhydride of a dicarboxylic acid,preferably R¹ is derived from a compound selected from the groupconsisting of oxalic acid, malonic acid, succinic acid, glutaric acid,glutaconic acid, adipic acid, muconic acid, pimelic acid, phthalic acid,terephthalic acid, tetrahydrophthalic acid, malic acid, maleic acid,fumaric acid, suberic acid, mesaconic acid, sebacic acid, azelaic acid,tartaric acid, itaconic acid, glutinic acid, citraconic acid, brassylicacid, dodecanedioic acid, traumatic acid, thapsic acid, thecorresponding acid chlorides, methyl or ethyl esters or anhydrides ofthese compounds and mixtures thereof, more preferably R¹ is derived froma compound selected from the group consisting of oxalic acid, malonicacid, succinic acid, glutaric acid, adipic acid, pimelic acid, phthalicacid, tetrahydrophthalic acid, malic acid, tartaric acid, thecorresponding acid chlorides, methyl or ethyl esters or anhydrides ofthese compounds and mixtures thereof, and most preferably adipic acid;

R² is derived from a fatty amine selected from the group consisting of2-ethylhexylamine, 2-propylheptylamine, n-octylamine, n-decylamine,n-dodecylamine, (coco alkyl)-amine, (palm oil alkyl) amine,n-tetradecylamine, n-hexadecylamine, n-octadecylamine, oleylamine,(tallow alkyl)-amine, (hydrogenated tallow alkyl)-amine, (rape seedalkyl)-amine, (soya alkyl)-amine, erucyl amine,N-(n-decyl)-N-methyl-trimethylene-diamine,N-(n-dodecyl)-N-methyl-trimethylene-diamine, N-(cocoalkyl)-N-methyl-trimethylene-diamine, N-(rape seedalkyl)-N-methyl-trimethylene-diamine, N-(soyaalkyl)-N-methyl-trimethylene-diamine, N-(tallowalkyl)-N-methyl-trimethylene-diamine, N-(hydrogenated tallowalkyl)-N-methyl-trimethylene-diamine,N-(erucyl)-N-methyl-trimethylene-diamine, isotridecyloxypropylamine andmixtures thereof, preferably (coco alky)-amine or (tallow alkyl)-amine;

R³ is derived from an alkylating agent selected from the groupconsisting of dimethyl sulphate, diethyl sulphate, dimethyl carbonate,benzyl chloride, methyl bromide, methyl chloride, methyl iodide,preferably dimethyl sulphate or methyl chloride and mixtures thereof.

According to another embodiment the compound of formula (1a) possessesthe following characteristics:

R¹ is derived from a compound selected from the group consisting ofadipic acid, maleic anhydride, sebacic acid and glutaric acid;

R² is derived from an ethoxylated fatty amine selected from the groupconsisting of ethoxylated (C₁₆-C₁₈) and C₁₈-unsaturated alkylamine,ethoxylated (C₈-C₁₆) and C₁₈-unsaturated alkylamine, ethoxylated (cocoalkyl)-amine, ethoxylated oleylamine, ethoxylated (tallow alkyl)-amineand ethoxylated (palm oil alkyl)-amine; and

R³ is derived from an alkylating agent selected from the groupconsisting of dimethyl sulphate, diethyl sulphate and methyl chloride,and preferably is methyl chloride.

According to another embodiment, the collector agent of step b) consistsof one or more compounds of formula (1) and/or (1a).

According to another embodiment, the aqueous suspension obtained in stepc) has a pH from 7 to 10, preferably from 7.5 to 9.5 and more preferablyfrom 8.5 to 9.

According to another embodiment, the collector agent is added in step c)in an amount of from 1 to 5,000 ppm based on the total dry weight of thewhite pigment and impurities containing material of step a), preferablyin an amount of from 20 to 2,000 ppm, more preferably in an amount offrom 30 to 1,000 ppm, and most preferably in an amount of from 50 to 800ppm based on the total dry weight of said white pigment and impuritiescontaining material of step a).

According to another embodiment, the aqueous suspension obtained in stepc) has a solids content of between 5 and 80 wt.-% based on the totalweight of the solids in the suspension, preferably of between 10 and 70wt.-%, more preferably of between 20 and 60 wt.-% and most preferably ofbetween 25 and 55 wt.-% based on the total weight of the solids in thesuspension.

According to another embodiment, one or more additives are added to theaqueous suspension prior to, during or after step c), wherein theadditives are selected from the group comprising pH-adjusting agents,solvents, depressants, polyelectrolytes, frothers and collector agentsother than the collector agents according to formula (1) and/or (1a).

According to another embodiment, the aqueous suspension obtained in stepc) is ground during and/or after step c).

According to another embodiment, the gas in step d) is air.

According to another embodiment, the suspension in step d) has atemperature of between 5 and 40° C., preferably between 10 and 40° C.,more preferably between 10 and 30° C. and most preferably between 15 and25° C.

According to another embodiment, the white pigment bearing phaseobtained from step e) is dispersed and/or ground before and/or afterstep e) and preferably is dispersed and/or ground in the presence of atleast one dispersing agent and/or at least one grinding aid agent.

According to another embodiment, the white pigment containing productcomprises at least 95 wt.-% white pigment, based on the dry weight,preferably of at least 98 wt.-%, more preferably of at least 99 wt.-%and most preferably of at least 99.9 wt.-% based on the dry weight.

According to another embodiment a process for manufacturing whitepigment containing products is provided, characterised in that saidprocess comprises the following steps:

-   -   a) providing at least one white pigment and impurities        containing material;    -   b) providing at least one collector agent selected from the        group consisting of compounds of formula (1):

-   -   R¹ is selected from the group consisting of a direct bond, an        alkylene radical having from 1 to 10 carbon atoms, a substituted        alkylene radical, wherein said alkylene radical is substituted        by 1 or 2 —OH groups, a cycloalkylene group, a cycloalkenylene        group and an arylene group;    -   R² is selected from the group consisting of a hydrocarbyl group        having from 8 to 24 carbon atoms or a group of formula        R⁴—O-(A′O)_(w)-T-, wherein;        -   R⁴ represents a hydrocarbyl group having from 8 to 24 carbon            atoms;        -   w is a number within the range from 0 to 20;        -   A′O is an alkyleneoxy group having from 2 to 4 carbon atoms;            and        -   T represents an alkylene group having from 1 to 6 carbon            atoms;    -   R³ is selected from the group consisting of a hydrocarbyl group        or a benzyl group;    -   AO represents an alkyleneoxy group having from 2 to 4 carbon        atoms;    -   X represents an anion derived from an alkylating agent R³X;    -   x is a number within the range from 1 to 20;    -   p is a number within the range from 1 to 15;    -   t is 0 or 1;    -   y is 0 or 1; and    -   G represents a group of formula (2);

-   -   wherein;    -   B represents an alkyl group having from 1 to 4 carbon atoms or        represents a benzyl group;    -   s is 1, 2 or 3;    -   R³, X and t are as defined above;    -   N⁺ is connected to R² in formula (1); and    -   (CH₂)_(s) is connected to the quaternary nitrogen atom in        formula (1);    -   c) mixing said white pigment and impurities containing material        of step a) and said collector agent of step b) in an aqueous        environment to form an aqueous suspension;    -   d) passing gas through the suspension formed in step c);    -   e) recovering the white pigment containing product by removing        the white pigment bearing phase from the aqueous suspension        obtained after step d).

A “pigment” in the meaning of the present invention is a solid colouringmaterial having a defined chemical composition and a characteristiccrystalline structure. Pigments can be inorganic pigments. Pigments maybe synthetic or natural pigments. Furthermore, pigments are insoluble inwater and, thus, resulting in a suspension when contacting them withwater.

A “white pigment” in the meaning of the present invention is a pigmentthat has a white appearance when illuminated by daylight.

A “white mineral pigment” in the meaning of the present invention is aninorganic white pigment that may be obtained naturally and specificallyincludes natural calcium carbonate or ground calcium carbonate (inparticular limestone, chalk, marble, calcite), calciumcarbonate-comprising mineral material (may be with a 70 wt.-% minimumcontent of CaCO₃, based on the weight of the mineral), dolomite, barite,aluminium oxide, titanium dioxide and mixtures of the foregoing.

An “alkaline earth metal carbonate” in the meaning of the presentinvention is a carbonate that comprises at least one alkaline earthmetal cation. The alkaline earth metals according to the presentinvention are beryllium Be²⁺, magnesium Mg²⁺, calcium Ca²⁺, strontiumSr²⁺, barium Ba²⁺ and radium Ra²⁺.

“Calcium carbonate” in the meaning of the present invention includesnatural calcium carbonate and may be a ground calcium carbonate (GCC).

“Natural calcium carbonate” in the meaning of the present invention is acalcium carbonate (calcite) obtained from natural sources, such asmarble, limestone, or chalk.

“Ground calcium carbonate” (GCC) in the meaning of the present inventionis a natural calcium carbonate that is processed through a wet and/ordry treatment such as grinding, screening and/or fractionating, forexample by a cyclone or classifier. “Impurities” in the meaning of thepresent invention are substances that differ from the chemicalcomposition of the desired white pigment.

A “collector agent” in the meaning of the present invention is achemical compound that is adsorbed by the envisaged particles either bychemisorption or by physisorption. The collector agent renders thesurface of the impurities more hydrophobic.

A “gas” in the meaning of the present invention is a sample of matterthat conforms to the shape of a container in which it is held andacquires a uniform density inside the container, even in the presence ofgravity and regardless of the amount of substance in the container. Ifnot confined to a container, gaseous matter, also known as vapour, willdisperse into space. The term gas is also used in reference to thestate, or condition, of matter having this property. A gas is composedof molecules that are in constant random motion. According to thepresent invention the compound has to be in a gaseous state at roomtemperature (20±2° C.) and at standard atmospheric pressure (101,325 Paor 1.01325 bar).

A “suspension” or “slurry” in the meaning of the present inventioncomprises non-dissolved solids in an aqueous medium, and optionallyfurther additives, and usually contains large amounts of solids and,thus, is more viscous and can be of higher density than the aqueousmedium supporting the suspension.

The “particle size” of fine (i.e. a d₅₀<5 μm) white pigment andimpurities containing material herein is described by its distributionof particle sizes d_(x). Therein, the value d_(x) represents thediameter relative to which x % by weight of the particles have diametersless than d_(x). This means that, for example, the d₂₀ value is theparticle size at which 20 wt.-% of all particles are smaller than thatparticle size. The d₅₀ value is thus the weight median particle size,i.e. 50 wt.-% of all grains are bigger and the remaining 50 wt.-% aresmaller than this particle size. For the purpose of the presentinvention the particle size of fine (i.e. a d₅₀<5 μm) white pigment andimpurities containing material is specified as weight median particlesize d₅₀ unless indicated otherwise. The d₉₈ value is the particle sizeat which 98 wt.-% of all particles are smaller than that particle size.Fine particle sizes (i.e. a d₅₀<5 μm) were determined by using aSedigraph™ 5100 or 5120 instrument of Micromeritics InstrumentCorporation. The method and the instrument are known to the skilledperson and are commonly used to determine the particle size of fillersand pigments. The measurements were carried out in an aqueous solutionof 0.1 wt.-% Na₄P₂O₇. The samples were dispersed using a high speedstirrer and sonicated.

The “particle size” of a coarse (i.e. a d₅₀ above 5 μm) white pigmentand impurities containing material herein is described by itsdistribution of particle sizes d_(x). Therein, the value d_(x)represents the diameter relative to which x % by weight of the particleshave diameters less than d_(x). This means that, for example, the d₂₀value is the particle size at which 20 wt.-% of all particles aresmallerthan that particle size. The d₅₀ value is thus the weight medianparticle size, i.e. 50 wt.-% of all grains are bigger and the remaining50 wt.-% are smaller than this particle size. For the purpose of thepresent invention the particle size of coarse (i.e. a d₅₀>5 μm) whitepigment and impurities containing material is specified as weight medianparticle size d₅₀ unless indicated otherwise. The d₉₈ value is theparticle size at which 98 wt.-% of all particles are smaller than thatparticle size. Coarse particle sizes (i.e. a d₅₀>5 μm) were determinedby using a Malvern Mastersizer 2000 Laser Diffraction System from thecompany Malvern, UK. The raw data obtained by the measurement areanalysed using the Mie theory, with a defined RI (particle refractiveindex) of 1.57 and iRI (absorption index) of 0.005 and MalvernApplication Software 5.60. The measurement was performed with an aqueousdispersion. For this purpose, the samples were dispersed using ahigh-speed stirrer. The weight determined particle size distribution maycorrespond to the volume determined particle size if the density of allthe particles is equal.

A “specific surface area (SSA)” of a calcium carbonate product in themeaning of the present invention is defined as the solids surface areaof a bulk dray sample, representative of all the distribution ofparticles present, divided by the mass of the bulk sample. As usedherein the specific surface area is measured by adsorption using the BETisotherm (ISO 9277:2010) and is specified in m²/g.

A “conventional flotation process” or a “direct flotation process” inthe meaning of the present invention is a flotation process in which thedesirable white pigments are directly floated and collected from theproduced froth leaving behind a suspension containing the impurities.

A “reverse flotation process” or “indirect flotation process” in themeaning of the present invention is a flotation process in which theimpurities are directly floated and collected from the produced frothleaving behind a suspension containing the desired white pigments.

The inventive process for manufacturing white pigment containingproducts involves the provision of at least one “white pigment andimpurities containing material” and at least one inventive collectoragent. Said white pigment and impurities containing material and saidcollector agent are mixed in an aqueous environment to form an aqueoussuspension. Afterwards or during mixing a gas is passed through theobtained aqueous suspension and the white pigment containing product isrecovered by removing the white pigment bearing phase from the aqueoussuspension obtained after passing the gas through the suspension.

In the following, details and preferred embodiments of the process formanufacturing white pigment containing products will be set out in moredetail. It is to be understood that these embodiments or details applyalso for the white pigments containing product obtained by the inventiveprocess and for the inventive use of the white pigment bearing phasealso obtained by the inventive process.

The White Pigment and Impurities Containing Material

Step a) of the process of the invention refers to the provision of atleast one white pigment and impurities comprising mineral.

A white pigment in the meaning of the present invention is a pigmentthat has a white appearance when viewed in daylight. The white nature ofthe white pigments is predominately based on the relatively Low lightabsorption in combination with an unselective light scattering of thevisual light at the pigment-air interface. The white pigments accordingto the present invention are inorganic white pigments that may beobtained naturally and synthetically and specifically include naturalcalcium carbonate or ground calcium carbonate (in particular limestone,chalk, marble, calcite), calcium carbonate-comprising mineral material(can be with a 50 wt.-% minimum content of CaCO₃, based on the weight ofthe mineral), dolomite, barite, aluminium oxide, titanium dioxide andmixtures of the foregoing.

White pigments may be white mineral pigments. White mineral pigments inthe meaning of the present invention are inorganic white pigments thatmay be obtained naturally. Beside the above mentioned natural calciumcarbonate or ground calcium carbonate (in particular limestone, chalk,marble, calcite), calcium carbonate-comprising mineral material (can bewith a 50 wt.-% minimum content of CaCO₃, based on the weight of themineral), dolomite, barite, and mixtures of the foregoing, the whitemineral pigments include aluminium oxide Al₂O₃ containing minerals, forexample γ-Al₂O₃ having a cubic structure and α-Al₂O₃ having arhombohedral (trigonal) structure. Additionally, the aluminium oxidecontaining minerals may comprise other elements such as for examplesodium in Na₂O·11Al₂O₃, commonly known as diaoyudaoit. Other inventivewhite mineral pigments are titanium dioxide TiO₂ containing minerals,for example rutile, anatase or brookite. Further white mineral pigmentsare white oxide minerals such as barium sulphate (BaSO₄), zinc oxide(ZnO), zirconium dioxide (ZrO₂), or tin dioxide (SnO₂), or whitesulphate minerals and white sulphide minerals such as zinc sulphide(ZnS) or lead carbonate (PbCO₃).

Preferably, the white mineral pigment is au alkaline earth metalcarbonate.

Alkaline earth metal carbonates in the meaning of the present inventionare carbonates that comprise at least one alkaline earth metal cation.The alkaline earth metals according to the present invention areberyllium Be²⁺, magnesium Mg²⁺, calcium Ca²⁺, strontium Sr²⁺, bariumBa²⁺ and radium Ra²⁺ and, preferably, magnesium and calcium. Thealkaline earth metal carbonates in the meaning of the present inventionare, for example, beryllium carbonate, magnesium carbonate, calciumcarbonate, strontium carbonate, barium carbonate or radium carbonate.

According to one embodiment of the present invention, the alkaline earthmetal carbonate consist of only one alkaline earth metal, for example,calcium. The alkaline earth metal carbonate may alternatively consist ofa mixture of two alkaline earth metals as for example calcium andmagnesium and, thus, the alkaline earth metal carbonate may be a calciummagnesium carbonate, e.g., dolomite. The alkaline earth metal carbonatemay comprise a mixture of two or more alkaline earth metals.Additionally, the alkaline earth metal carbonate may comprise furthercations as for example sodium in gaylussite (sodium calcium carbonate).

The white pigment may comprise more than one alkaline earth metalcarbonate. For example, the white pigment may comprise one magnesiumcarbonate and one calcium carbonate. Alternatively, the white pigmentmay consist of only one alkaline earth metal carbonate.

The white pigment may comprise a mixture of two or more white mineralpigments. For example the white pigment may comprise one alkaline earthmetal carbonate and an inorganic white pigment that is selected from thegroup consisting of aluminium dioxide, titanium dioxide, bariumsulphate, zinc oxide, zirconium dioxide, or tin dioxide, white sulphateor sulphide minerals.

Preferably, the alkaline earth metal carbonate may be a calciumcarbonate.

Calcium carbonate or natural calcium carbonate is understood to be anaturally occurring form of calcium carbonate, mined from sedimentaryrocks such as limestone or chalk, or from metamorphic marble rocks.Calcium carbonate is known to exist as three types of crystalpolymorphs: calcite, aragonite and vaterite. Calcite, the most commoncrystal polymorph, is considered to be the most stable crystal form ofcalcium carbonate. Less common is aragonite, which has a discrete orclustered needle orthorhombic crystal structure. Vaterite is the rarestcalcium carbonate polymorph and is generally unstable. Calcium carbonateis almost exclusively of the calcitic polymorph, which is said to betrigonal-rhombohedral and represents the most stable of the calciumcarbonate polymorphs. The term “source” of the calcium carbonate in themeaning of the present application refers to the naturally occurringmineral material from which the calcium carbonate is obtained. Thesource of the calcium carbonate may comprise further naturally occurringcomponents such as magnesium carbonate, aluminium oxide etc.

The source of calcium carbonate may be selected from marble, chalk,calcite, dolomite, limestone, or mixtures thereof. Preferably, thesource of calcium carbonate may be selected from marble.

Preferably, the alkaline earth metal carbonate may be a ground calciumcarbonate (GCC). Ground calcium carbonate (GCC) is understood to beobtained by grinding the calcium carbonate either dry or alternativelywet followed by a subsequent drying step.

In general, the grinding step can be carried out with any conventionalgrinding device, for example, under conditions such that refinementpredominantly results from impacts with a secondary body, i.e. in one ormore of: a ball mill, a rod mill, a vibrating mill, a roll crusher, acentrifugal impact mill, a vertical bead mill, an attrition mill, a pinmill, a hammer mill or other such equipment known to the skilled man. Incase calcium carbonate containing mineral powder comprises a wet groundcalcium carbonate containing mineral material, the grinding step may beperformed under conditions such that autogenous grinding takes placeand/or by horizontal ball milling, and/or other such processes known tothe skilled man. The wet processed ground calcium carbonate containingmineral material thus obtained may be dewatered by well-known processes,e.g. by filtration, centrifugation or forced evaporation prior todewatering. An additional step of drying may be carried out in a singlestep such as spray drying, or in at least two steps.

Preferably, the white pigment may consist of only one ground calciumcarbonate. Alternatively, the white pigment may consist of a mixture oftwo ground calcium carbonates selected from different sources of groundcalcium carbonate. The white pigment may also comprise a mixture of twoor more ground calcium carbonates selected from different sources ofground calcium carbonate. For example, the white pigment may compriseone GCC selected from dolomite and one GCC selected from calcite marble.Additionally to the GCC the white pigment may comprise further whitemineral pigments.

The white pigment and impurities containing material will contain whitepigments as defined above and impurities. Impurities in the meaning ofthe present invention are substances that differ from the chemicalcomposition of the white pigment and, therefore, are no white pigments.

The impurities to be removed or reduced by the process according to thepresent invention are compounds that have, for example a grey, black,brown, red, or yellow colour or any other colour affecting the whiteappearance of the white pigment material. Alternatively, the impuritiesto be removed or reduced have a white colour but have different physicalproperties than the white pigments and, therefore, adversely affect thewhite pigments.

According to a preferred embodiment the starting material, e.g., thewhite pigment and impurities containing material may comprise impuritiesselected from iron sulphides.

Iron sulphides or iron sulphates in the meaning of the present inventionare understood to be chemical compounds of iron and sulphur comprising awide range of stochiometric formulae and different crystallinestructures. For example the iron sulphide can be iron(II) sulphide FeS(magnetopyrite) or pyrrhotite Fe_(1−x)S wherein x is from 0 to 0.2. Theiron sulphide can also be an iron(II) disulphide FeS₂ (pyrite ormarcasite). The iron sulphides can also contain other elements then ironand sulphur as for example nickel in the form of mackinawite (Fe,Ni)_(1+x)S wherein x is from 0 to 0.1.

The impurities in the white pigment and impurities containing materialmay also be iron oxides.

Iron oxides in the meaning of the present invention are understood to bechemical compounds composed of iron and oxide. Iron oxide comprises, forexample iron(II) oxide FeO, also known as wüstite, iron(I, III) oxidesFe₃O₄, also known as magnetite and iron(III) oxide Fe₂O₃. The ironoxides include also iron hydroxides and iron oxyhydroxides that containbeneath the elements iron and oxygen, the additional element hydrogen.Iron hydroxide comprises, for example iron(II) hydroxide Fe(OH)₂ andiron(III) hydroxide Fe(OH)₃, also known as bernalite. Iron oxyhydroxidecomprises, for example α-FeOOH also known as goethite forming prismaticneedle-like crystals, γ-FeOOH also known as lepidocrocite formingorthorhombic crystal structures, δ-FeOOH also known as feroxyhytecrystallizing in the hexagonal system and ferrihydrite FeOOH·0.4H₂O. Theiron oxides can also contain additional elements as, for example,sulphur in Fe₈O₈(OH)₆(SO₄)·nH₂O also known as schwertmannite or chloridein FeO(OH,Cl) also known as akaganeite.

The white pigment and impurities containing material may compriseimpurities that are selected from graphite.

Graphite in the meaning of the present invention is understood to be anallotrope of carbon. There are three principal types of naturalgraphite: crystalline flake graphite, amorphous graphite and lumpgraphite. Crystalline flake graphite (or flake graphite for short)occurs as isolated, flat, plate-like particles with hexagonal edges ifunbroken and, when broken, the edges can be irregular or angular.Amorphous graphite occurs as fine particles and is the result of thermalmetamorphism of coal, the last stage of coalification, and is sometimescalled meta-anthracite. Very fine flake graphite is sometimes calledamorphous in the trade. Lump graphite (also called vein graphite) occursin fissure veins or fractures and appears as massive platy intergrowthsof fibrous or acicular crystalline aggregates.

Alternatively the impurities in the white pigment and impuritiescontaining material may be silicates. The silicates may be colouring orabrasive.

Silicates or silicate minerals in the meaning of the present inventionare understood to be compounds that comprise silicon and oxygen.Additionally, the silicates can comprises further ions such as forexample aluminium ions, magnesium ions, iron ions or calcium ions. Thesilicates and silicate minerals can be selected from neosilicates,sorosilicates, cyclosilicates, inosilicates, phyllosilicates, andtectosilicates and amorphous silicates. Neosilicates are silicateminerals in which the SiO₄ tetrahedra are isolated and have metal ionsas neighbours. Commonly known neosilicates are zircon, willemite,olivine, mullite, forsterite, aluminosilicates or fayalite.Sorosilicates are silicate minerals which have isolated doubletetrahedral groups with a silicon to oxygen ratio of 2:7. Commonly knownsorosilicates are ilavite, gehlenite, epidote or kornerupine.Cyclosilicates are ring silicates that contain rings of linked SiO₄tetrahedra wherein the silicon to oxygen ratio is 1:3. Commonly knowncyclosilicates are benitonite, beryl or tourmaline. Inosilicates orchain silicates are silicate minerals which have interlocking chains ofsilicate tetrahedra with either SiO₃ in a 1:3 ratio for single chains orSi₄O₁₁ in a 4:11 ratio for double chains. Commonly known inosilicatesare enstatite, wollastonite, rhodenite, diopside or amphibolite as forexample grunerite, cummingtonite, actinolithe or hornblende.Phyllosilicates are sheet silicates that form parallel sheets ofsilicate tetrahedra with Si₂O₅ or a silicon oxygen ration of 2:5.Commonly known phyllosilicates are clay minerals, for example talc,kaoline, kaolinitic clay, calcined kaolinitic clay, halloysite, dickite,vermiculite, nontronite, sepiolite or montmorillonite, mica minerals,for example, biotite, muscovite, phlogopite, lepidolite or glauconite,or a chlorite mineral, for example clinochlore. Tectosilicates orframework silicates have a three-dimensional framework of silicatetetrahedra with SiO₂ tetrahedra or a silicon oxygen ration of 1:2.Commonly known tectosilicates are quartz minerals as for example quartz,tridymite and cristobalite, feldspar minerals as for example potassiumfeldspars comprising orthoclase and microline, sodium or calciumfeldspars comprising plagioclase, albite and andesine or scapolite andzeolithe. Amorphous silicates are for example diatomaceous earth oropale.

The silicate may be selected from the group consisting of quartz, amica, an amphibolite, a feldspar, a clay mineral and mixtures thereofand, preferably, may be quartz.

The inventive process is especially contemplated for separating whitepigments from impurities that consist of quartz and/or additionalsilicates.

Preferably the impurity in the white pigments and impurities containingmaterial consists only of quartz.

Alternatively, the impurity or impurities in the white pigment andimpurities containing material may comprise silicates that have a whitecolour. For example, the impurities may comprise silicates such aswollastonite, kaolin, kaolinitic clay, calcined kaolinitic clay,montmorillonite, talc, diatomaceous earth or sepiolite. In a preferredembodiment of the invention, the impurity consists of silicates thathave a white colour and more preferably the impurity consists of onlyone white coloured silicate. For example, the impurity may consist onlyof wollastonite, kaolin, kaolinitic clay, calcines kaolinitic clay,montmorillonite, talc, diatomaceous earth or sepiolite. These impuritiesobtained and separated according to the inventive flotation method maybe further processed and used in suitable applications. The impuritiescontaining only white coloured silicates and, preferably containing onlyone white coloured silicate obtained by the inventive process may beused in the same way than the white pigment containing product.

In a preferred embodiment, the amount of white pigment in the whitepigment and impurities containing material of step a) may be from 0.1 to99.9 wt.-%, based on the dry weight, preferably from 30 to 99.7 wt.-%,more preferably from 60 to 99.3 wt.-% and most preferably from 80 to 99wt.-%, based on the dry weight.

In another preferred embodiment, the weight ratio of whitepigment:impurities in the white pigment and impurities containingmaterial of step a) may be from 0.1:99.9 to 99.9:0.1, based on the dryweight, preferably from 30:70 to 99.7:0.3, more preferably from 60:40 to99.3:0.7, and most preferably from 80:20 to 99:1, based on the dryweight.

The total amount of the white pigment and the impurities in the whitepigment and impurities containing material of step a) may represent atleast 90 wt.-% relative to the total weight of the white pigment andimpurities containing material, preferably at least 95 wt.-%, morepreferably at least 98 wt.-%, and most preferably at least 99 wt.-%relative to the total weight of the white pigment and impuritiescontaining material.

As set out before, in a preferred embodiment the impurity in the whitepigment and impurities containing material may consist of a silicate. Inthis case, the total amount of the white pigment and the silicate in thewhite pigment and impurities containing material of step a) representsat least 90 wt.-% relative to the total weight of the white pigment andimpurities containing material, preferably at least 95 wt.-%, morepreferably at least 98 wt.-%, and most preferably for at least 99 wt.-%.

Alternatively, the white pigment and impurities containing material mayconsist of white pigment and silicate. Preferably, the white pigment andimpurities containing material may consist of white pigment and quartz.Alternatively, the white pigment and impurities containing material mayconsist of white pigment and a white coloured silicate that is selectedfrom the group consisting of wollastonite, kaolin, kaolinitic clay,calcines kaolinitic clay, montmorillonite, talc, diatomaceous earth orsepiolite.

The white pigment and impurities containing material of step a) may havea weight median grain diameter in the range of from 1 to 1,000 μm,preferably of from 3 to 700 μm, more preferably of from 5 to 500 μm andmost preferably of from 10 to 80 μm or from 100 to 400 μm.

In another preferred embodiment the white pigment and impuritiescontaining material of step a) may have a weight median grain diameterin the range of from 1 to 1,000 μm, preferably of from 3 to 500 μm, morepreferably of from 5 to 100 μm and most preferably of from 10 to 80 μmif the subsequent flotation process is a standard flotation process. Astandard flotation process in the meaning of the present invention is aflotation process that is performed after grinding and/or classificationof the white pigment and impurities containing material.

In another preferred embodiment the white pigment and impuritiescontaining material of step a) may have a weight median grain diameterin the range of from 1 to 1,000 μm, preferably of from 10 to 700 μm,more preferably of from 50 to 500 μm and most preferably of from 100 to400 μm if the subsequent flotation process is a coarse flotationprocess. A coarse flotation process in the meaning of the presentinvention is a flotation process that is performed within the firstgrinding loop of the white pigment and impurities containing material.

The Collector Agent

Step b) of the process of the present invention refers to the provisionof at least one collector agent.

A collector agent in the meaning of the present invention is a chemicalcompound that is adsorbed by the envisaged particles either bychemisorption or by physisorption. The collector agents according to thepresent invention have the general formula (1),

wherein;

R¹ is selected from the group consisting of

-   -   i) a direct bond,    -   ii) a C₁-C₂₀, linear or branched, saturated or unsaturated        hydrocarbon chain optionally substituted by one or more —OH        group(s), one or more methyl and/or methylene groups, a        cycloalkylene group, a cycloalkenylene group and/or an arylene        group, preferably        -   A) an alkylene radical having from 1 to 20, more preferably            from 1 to 10 carbon atoms, most preferably a substituted            alkylene radical, wherein said substituted alkylene radical            is substituted by 1 or 2 —OH groups, 1 or 2 methyl and/or            methylene groups, a cycloalkylene group, a cycloalkenylene            group and/or an arylene group, or        -   B) an alkenylene radical having from 1 to 20, preferably            from 1 to 10 carbon atoms, more preferably a substituted            alkenylene radical, wherein said substituted alkenylene            radical is substituted by 1 or 2 —OH groups, 1 or 2 methyl            and/or methylene groups, a cycloalkylene group, a            cycloalkenylene group and/or an arylene group;

R² is selected from the group consisting of a hydrocarbyl group havingfrom 8 to 24 carbon atoms or a group of formula R⁴—O-(A′O)_(w)-T-,wherein;

R³ represents a hydrocarbyl group having from 8 to 24 carbon atoms;

w is a number within the range from 0 to 20;

A′O is an alkyleneoxy group having from 2 to 4 carbon atoms; and

T represents an alkylene group having from 1 to 6 carbon atoms;

R³ is selected from the group consisting of a hydrocarbyl group or abenzyl group;

AO represents an alkyleneoxy group having from 2 to 4 carbon atoms;

X represents an anion derived from an alkylating agent R⁴X;

x is a number within the range from 1 to 20;

p is a number within the range from 1 to 15;

t is 0 or 1;

y is 0 or 1; and

G represents a group of formula (2);

wherein;

B represents an alkyl group having from 1 to 4 carbon atoms orrepresents a benzyl group;

s is 1, 2 or 3;

R³, X and t are as defined above;

N⁺ is connected to R² in formula (1); and

(CH₂)₃ is connected to the quaternary nitrogen atom in formula (1);

In a preferred embodiment the compound according to general formula (1)is the compound according to formula (1a).

wherein, AO, p, t, x, R¹, R², R³ and X are as defined above.

It is to be understood that the nitrogen atom in formula (1) and (1a)has a positive charge when t=1 but is neutral when t=0.

The compounds of formula (1) and (1a) may be prepared according to knownpreparations techniques.

For example, compounds of formula (1) and (1a) may be easily obtained bycondensation of a dicarboxylic acid or a derivative thereof having theformula (1a) or (Ib),

where D- is —OH, —Cl or —OR′, where R′ is a C₁-C₄ alkyl group; R¹ isselected from the group consisting of

-   -   i) a direct bond,    -   ii) a C₁-C₂₀, linear or branched, saturated or unsaturated        hydrocarbon chain optionally substituted by one or more —OH        group(s), one or more methyl and/or methylene groups, a        cycloalkylene group, a cycloalkenylene group and/or an arylene        group, preferably        -   A) an alkylene radical of formula —(CH₂)₂—, in which z is an            integer from 1 to 20, more preferably from 1 to 10, even            more preferably from 2 to 6 and even more preferably 4, most            preferably a substituted alkylene radical, wherein said            substituted alkylene radical is substituted by 1 or 2 —OH            groups, 1 or 2 methyl and/or methylene groups, a            cycloalkylene group, a cycloalkenylene group and/or an            arylene group, or        -   B) an alkenylene radical having from 1 to 20, preferably            from 1 to 10 carbon atoms, more preferably a substituted            alkenylene radical, wherein said substituted alkenylene            radical is substituted by 1 or 2 —OH groups, 1 or 2 methyl            and/or methylene groups, a cycloalkylene group, a            cycloalkenylene group and/or an arylene group;

with an alkoxylated fatty amine having the formula (II),

wherein R² is selected from the group consisting of a hydrocarbyl grouphaving 8 to 24 carbon atoms, preferably 12 to 24 carbon atoms or a groupof formula R⁴—O-(A′O)_(w)-T-, wherein;

R⁴ represents a hydrocarbyl group having from 8 to 24 carbon atoms,preferably 12 to 24 carbon atoms;

w is a number within the range from 0 to 20, preferably from 0 to 10 andmore preferably from 0 to 3;

A′O is an alkyleneoxy group having from 2 to 4 carbon atoms;

T represents an alkylene group having from 1 to 6 carbon atoms;preferably from 1 to 4 carbon atoms and most preferably from 2 to 3carbon atoms;

AO represents an alkyleneoxy group having from 2 to 4 carbon atoms,preferably 2 carbon atoms;

B represents an alkyl group having from 1 to 4 carbon atoms orrepresents a benzyl group;

x represents a number within the range from 1 to 20, preferably withinthe range from 1 to 10, more preferably between the range from 1 to 6;

s is 1, 2 or 3, preferably 2 or 3;

y is 0 or 1;

for the preparation of compound (1a) the preferred alkoxylated fattyamine has the formula (IIa),

wherein, AO, x and R² are as defined above;

or of a product obtainable by partial or total quaternisation of thealkoxylated fatty amine of formula (II) or (IIa); optionally saidreaction between the dicarboxylic acid according to formula (I) and thealkoxylated fatty amine according to formula (II) or (IIa) is beingfollowed by a further reaction step wherein part or all of the nitrogenatoms are quaternised by reaction with an alkylating agent R³X, where R³is a hydrocarbyl group, preferably a C₁-C₄ alkyl group or the benzylgroup, and X is an anion derived from the alkylating agent R³X.

It is to be understood that when a compound of formula (II) or (IIa)contains more than one (AO)_(x) group, the value of the integers x maybe the same or different, independently from one another. Similarly,when more than one y is present, all “y” are, independently form oneanother, identical or different.

The esterification condensation reactions taking place between thecompounds of formula (1a) or formula (Ib) and formula (II) or formula(IIa) are well-known in the art. The reactions are preferably beingperformed in the presence of an esterification catalyst, such as aBrönstedt or Lewis acid, for example methanesulphonic acid,p-toluenesulphonic acid, hypophosphoric acid, citric acid or borontrifluoride (BF₃).

When a dicarboxylic acid derivative of formula (1a) is used, wherein Dis O—R′, the reaction is a transesterification, which alternativelycould be performed in the presence of an alkaline catalyst.Alternatively, other conventional techniques known by the person skilledin the art could be used starting from other derivatives of thedicarboxylic acids, such as from anhydrides or their acid chlorides.

The reactions could take place with or without solvents added. Ifsolvents are present during the reaction, the solvents should be inertto esterification, e.g. toluene or xylene.

The esterification condensation reaction between the compounds (Ia) or(Ib) and (II) or (IIa) is suitably effected by heating the mixture at atemperature between 120 and 280° C. for a period of from 2 to 20 hours,optionally at reduced pressure of from 5 to 200 mbar.

When t in formula (I) is 0 the product is a tertiary polyesteraminecompound, and when t is 1 the product is a polyester polyquaternaryammonium compound. Quaternisation is a reaction type that is well-knownin the art. For the quaternisation step, the alkylating agent R³X issuitably selected from the group consisting of dimethyl sulphate,diethyl sulphate, dimethyl carbonate, benzyl chloride, methyl bromide,methyl chloride, methyl iodide, preferably dimethyl sulphate or methylchloride and mixtures thereof.

The quaternisation may be performed on the condensation product ofcompounds, (Ia) or (Ib) and (II) or (IIa). It is also possible to carryout the quaternisation of the compound according to formula (II) or(IIa) in a first step and then carry out the esterification ofcompounds, (Ia) or (Ib) and quaternised (II) or (IIa). Either a part of,or all of, the nitrogen atoms may be quaternised by reaction with analkylating agent, e.g. methyl chloride or dimethyl sulphate, to obtain aproduct that is partly or totally quaternised. Also, the two processescan be combined such that first a partially quaternised compound isesterified and the resulting polyester is further quaternised.

Quaternisation reactions are normally performed in water or a solvent,such as iso-propanol or ethanol, or in mixtures thereof. Otheralternative solvents could be ethylene glycol monobutyl ether,di(ethylene glycol) monobutyl ether, and other ethylene- and propyleneglycols, such as monoethylene glycol and diethylene glycol. The reactiontemperature of the quaternising reaction is suitably in the range from20 to 100° C., preferably at least 40° C., more preferably at least 50°C. and most preferably at least 55° C., and preferably at most 90° C.

The expression “totally quaternised” in the meaning of the presentinvention means that “all of the nitrogen atoms are quaternised” or that“all nitrogen atoms of the product are quaternary” which means that thetotal amount of basic nitrogen per gram of compound is less than orequal to 0.2 mmol, preferably less than or equal to 0.1 mmol, morepreferably less than or equal to 0.05 mmol.

As a consequence the heating is preferably stopped when the amount ofbasic nitrogen is less or equal to 0.2 mmol/g, preferably less than orequal to 0.1 mmol/g, more preferably less than or equal to 0.05 mmol/gas can be e.g. measured by titration with 0.2N hydrochloric acid or anyother suitable method known in the art.

According to one preferred embodiment all nitrogen atoms of the productare quatemary.

In one embodiment the molar ratio between the dicarboxylic acid orderivative (Ia) or (Ib) and the alkoxylated fatty amine (II) or (IIa) is2:1 to 1:2, preferably 1.5:1 to 1:1.5, more preferably 1.4:1 to 1:1.4.

Preferred compounds according to formula (1a) and formula (Ib) areselected from the group consisting of oxalic acid, malonic acid,succinic acid, glutaric acid, glutaconic acid, adipic acid, muconicacid, pimelic acid, phthalic acid, terephthalic acid, tetrahydrophthalicacid, malic acid, maleic acid, fumaric acid, suberic acid, mesaconicacid, sebacic acid, azelaic acid, tartaric acid, itaconic acid, glutinicacid, citraconic acid, brassylic acid, dodecanedioic acid, traumaticacid, thapsic acid, the corresponding acid chlorides, methyl or ethylesters or anhydrides of these compounds and mixtures thereof, morepreferred compounds according to formula (Ia) and formula (Ib) areselected from the group consisting of oxalic acid, malonic acid,succinic acid, glutaric acid, adipic acid, pimelic acid, phthalic acid,tetrahydrophthalic acid, malic acid, tartaric acid, the correspondingacid chlorides, methyl or ethyl esters or anhydrides of these compoundsand mixtures thereof, and most preferred is adipic acid;

Preferred compounds according to formula (II) or (IIa) are prepared byalkoxylation of amines selected from the group consisting of2-ethylhexylamine, 2-propylheptylamine, n-octylamine, n-decylamine,n-dodecylamine, (coco alkyl)-amine, (palm oil alkyl) amine,n-tetradecylamine, n-hexadecylamine, n-octadecylamine, oleylamine,(tallow alkyl)-amine, (hydrogenated tallow alkyl)-amine, (rape seedalkyl)-amine, (soya alkyl)-amine, erucyl amine,N-(n-decyl)-N-methyl-trimethylene-diamine,N-(n-dodecyl)-N-methyl-trimethylene-diamine, N-(cocoalkyl)-N-methyl-trimethylene-diamine, N-(rape seedalkyl)-N-methyl-trimethylene-diamine, N-(soyaalkyl)-N-methyl-trimethylene-diamine, N-(tallowalkyl)-N-methyl-trimethylene-diamine, N-(hydrogenated tallowalkyl)-N-methyl-trimethylene-diamine,N-(erucyl)-N-methyl-trimethylene-diamine, isotridecyloxypropylamine andmixtures thereof, more preferred are (coco alley)-amine or (tallowalkyl)-amine.

In one embodiment fatty amines as mentioned above are alkoxylated with 2to 20, preferably 2 to 10 ethoxy units and/or 2 to 20, preferably 2 to10 propoxy units and/or 2 to 20, preferably 1 to 10 butoxy units toobtain compounds according to formula (II) or (IIa). Randomlyalkoxylated products of formula (II) or (IIa) can be obtained by usingmixtures of ethoxy units, propoxy units and butoxy units. Blocks can begenerated by adding the alkoxy units subsequently, for example firstadding ethoxy units then adding propoxy unit and then butoxy units. Thealkoxylation may be performed by any suitable method known in the art byusing e.g. an alkaline catalyst such as potassium hydroxide, or an acidcatalyst.

Examples of commercial products according to formula (II) or (IIa)include Noramox SD20, Noramox SD15, Noramox S11, Noramox S5, Noramox S7,Noramox S2, Noramox SH2, Noramox O2, Noramox O5, Noramox C2, Noramox C5and Noramox C15 all provided by CECA France. Other examples ofcommercial products of formula (II) include Tomamine® E-17-5 andTomamine® E-T-2 available from Air products.

Preferred alkylating agents R³X are selected from the group consistingof dimethyl sulphate, diethyl sulphate, dimethyl carbonate, benzylchloride, methyl bromide, methyl chloride, methyl iodide, and mixturesthereof more preferred are dimethyl sulphate or methyl chloride. X ispreferably a single- or double-charged anion.

In formula (1) and (1a) x is a number within the range from 1 to 20,preferably within the range from 1 to 10 and more preferably within therange from 1 to 6. The average value of p in formula (1) and (1a)depends on the molar ratios of the compounds according to formula (1a)or (Ib) and (II) or (IIa) and on the reaction conditions. In oneembodiment p is a number in the range from 1 to 15, preferably in therange from 1 to 10 and more preferably is in the range from 1 to 5.

According to one embodiment of the present invention the compounds offormula (1) or (1a) may have various radicals and therefore may comprisea mixture of different compounds of formula (1) or (1a).

Furthermore, molecules might be present in the product mixture that arenot completely esterified, but the products according to formula (1) or(1a) are the key compounds.

In one embodiment the compound of formula (1) or (1a) is characterizedas follows:

R¹ represents an alkylene radical having from 1 to 20, preferably from 1to 10 carbon atoms, more preferably having from 2 to 6 carbon atoms,even more preferably having 4 carbon atoms;

R² represents a hydrocarbyl group having from 8 to 24 carbon atoms,preferably having from 12 to 24 carbon atoms;

R³ represents a hydrocarbyl group having from 1 to 4 carbon atoms,preferably an alkyl group having 1 or 2 carbon atoms and more preferablyis a methyl group;

AO is an alkyleneoxy group, preferably an ethoxy group;

X is an anion derived from an alkylating agent R³X; preferably chlorideor sulphate

x is a number within the range from 1 to 15, preferably in the rangefrom 2 to 10 and more preferably is in the range from 1 to 6;

p is a number within the range 1 to 15; and

t is 0 or 1, preferably 1.

According to still another embodiment the compound of formula (1) or(1a) possesses at least one of the following characteristics:

R¹ is derived from a dicarboxylic acid, a dicarboxylic acid chloride, adiester of a dicarboxylic acid, an anhydride of a dicarboxylic acid,preferably R¹ is derived from a compound selected from the groupconsisting of oxalic acid, malonic acid, succinic acid, glutaric acid,glutaconic acid, adipic acid, muconic acid, pimelic acid, phthalic acid,terephthalic acid, tetrahydrophthalic acid, malic acid, maleic acid,fumaric acid, suberic acid, mesaconic acid, sebacic acid, azelaic acid,tartaric acid, itaconic acid, glutinic acid, citraconic acid, brassylicacid, dodecanedioic acid, traumatic acid, thapsic acid, thecorresponding acid chlorides, methyl or ethyl esters or anhydrides ofthese compounds and mixtures thereof, more preferably R′ is derived froma compound selected from the group consisting of oxalic acid, malonicacid, succinic acid, glutaric acid, adipic acid, pimelic acid, phthalicacid, tetrahydrophthalic acid, malic acid, tartaric acid, thecorresponding acid chlorides, methyl or ethyl esters or anhydrides ofthese compounds and mixtures thereof, and most preferably adipic acid;

R² is derived from a fatty amine selected flow the group consisting of2-ethylhexylamine, 2-propylheptylamine, n-octylamine, n-decylamine,n-dodecylamine, (coco alkyl)-amine, (palm oil alkyl) amine,n-tetradecylamine, n-hexadecylamine, n-octadecylamine, oleylamine,(tallow alkyl)-amine, (hydrogenated tallow alkyl)-amine, (rape seedalkyl)-amine, (soya alkyl)-amine, erucyl amine,N-(n-decyl)-N-methyl-trimethylene-diamine,N-(n-dodecyl)-N-methyl-trimethylene-diamine, N-(cocoalkyl)-N-methyl-trimethylene-diamine, N-(rape seedalkyl)-N-methyl-trimethylene-diamine, N-(soyaalkyl)-N-methyl-trimethylene-diamine, N-(tallowalkyl)-N-methyl-trimethylene-diamine, N-(hydrogenated tallowalkyl)-N-methyl-trimethylene-diamine,N-(erucyl)-N-methyl-trimethylene-diamine, isotridecyloxypropylamine andmixtures thereof, preferably (coco alky)-amine or (tallow alkyl)-amine;

R³ is derived from an alkylating agent selected from the groupconsisting of dimethyl sulphate, diethyl sulphate, dimethyl carbonate,benzyl chloride, methyl bromide, methyl chloride, methyl iodide andmixtures thereof, preferably dimethyl sulphate or methyl chloride.

According to still another embodiment the compound of formula (1a)possesses the following characteristics:

R¹ is derived from a compound selected from the group consisting ofadipic acid, maleic anhydride, sebacic acid and glutaric acid;

R² is derived from a ethoxylated fatty amine selected from the groupconsisting of ethoxylated (C₁₆-C₁₈) and C₁₈-unsaturated alkylamine,ethoxylated (C₈-C₁₆) and C₁₈-unsaturated alkylamine, ethoxylated (cocoalkyl)-amine, ethoxylated oleylamine, ethoxylated (tallow alkyl)-amineand ethoxylated (palm oil alkyl)-amine; and

R³ is derived from an alkylating agent selected from the groupconsisting of dimethyl sulphate, diethyl sulphate and methyl chloride,and preferably is methyl chloride.

According to a preferred embodiment of the present invention thecollector agent of step b) is a polymer of adipic acid with ethoxylatedcoco alkyl amine (also known as (coco alkyl)-amine) (5OE) which istotally quaternised with methyl chloride. Such a polymer is prepared inthe experimental section as CA1. According to another preferredembodiment of the present invention the collector agent of step b) is apolymer of adipic acid with ethoxylated tallow alkyl amine (also knownas (tallow alkyl)-amine) (5OE) which is totally quaternised with methylchloride. Such a polymer is prepared in the experimental section as CA2.According to another preferred embodiment of the present invention thecollector agent of step b) is a polymer of adipic acid with ethoxylatedtallow alkyl amine (also known as (tallow alkyl)-amine) (11OE) which istotally quaternised with methyl chloride. (OE) is the number of ethyleneoxide equivalents that have been reacted with the fatty alkyl amine.

Step C) of the Process of the Invention

Step c) of the process of the invention refers to mixing said whitepigment and impurities containing material of step a) and said collectoragent of step b), in an aqueous environment to form an aqueoussuspension.

According to one embodiment of the present invention the at least onewhite pigment and impurities containing material of step a) may bemixed, in a first step, with water, and then, the obtained suspensionmay be mixed with the collector agent of step b) to form an aqueoussuspension.

The collector agent of step b) may be mixed, in a first step, withwater, and then, the obtained suspension may be mixed with the at leastone white pigment and impurities containing material of step a) to forman aqueous suspension.

According to another embodiment of the present invention, the at leastone white pigment and impurities containing material of step a) and thecollector agent of step b) may be mixed in one step with water to forman aqueous suspension.

Preferably, mixing may be carried out using a wet mill, a mixing tank, afeeding pump or a flotation agitator for mixing the collector into theaqueous suspension.

The mixing may be carried out at room temperature, i.e. at 20° C.±2° C.,or at other temperatures. According to one embodiment the mixing may becarried out at a temperature from 5 to 40° C., preferably from 10 to 30°C. and most preferably from 15° C. to 25° C., or at other temperatures.Heat may be introduced by internal shear or by an external source or acombination thereof.

The solids content of the aqueous suspension obtained by the inventivemethod can be adjusted by the methods known to the skilled person. Toadjust the solids content of an aqueous white pigments and impuritiescontaining material comprising suspension, the suspension may bepartially or fully dewatered by a filtration, centrifugation or thermalseparation process. Alternatively, water may be added to the whitepigment and impurities containing material until the desired solidscontent is obtained. Additionally or alternatively, a suspension havingan appropriate lower content of a white pigment and impuritiescontaining material may be added to the aqueous suspension until thedesired solid content is obtained.

According to a preferred embodiment, of the present invention theaqueous suspension obtained in step c) has a solids content measured asdescribed in the Examples section hereafter of between 5 and 80 wt.-%based on the total weight of the solids in the suspension, preferably ofbetween 10 and 70 wt.-%, more preferably of between 20 and 60 wt.-% andmost preferably of between 25 and 55 wt.-%, based on the total weight ofthe solids in the suspension.

The aqueous suspension obtained in step c) may have a pH from 7 to 10,preferably from 7.5 to 9.5 and more preferably from 8.5 to 9.0.

The inventive collector agent(s) may be added in step c) in an amount offrom 1 to 5,000 ppm, based on the total dry weight of the mineralmaterial of step a), preferably in an amount of from 20 to 2,000 ppm,more preferably in an amount of from 30 to 1,000 ppm, and mostpreferably in an amount of from 50 to 800 ppm, based on the total dryweight of the mineral material of step a).

The amount of the inventive collector agent may be adjusted byconsidering the specific surface area of the impurities. According toone embodiment, the inventive collector agent may be added in step c) inan amount of from 1 to 100 mg per m² of impurities in said white pigmentcontaining material of step a), preferably in an amount of from 5 to 50mg per m² of impurities in said white pigment containing material ofstep a), and most preferably of from 10 to 45 mg per m² of impurities insaid white pigment containing material of step a). The specific surfacearea of the impurities is measured as described in the Examples sectionhereafter. Additionally to the white pigment and impurities containingmaterial a) and the collector agent b), one or more further additivesmay be present in the aqueous suspension. Possible additives are, forexample pH-adjusting agents, solvents (water, organic solvent(s) andmixtures thereof); depressants, such as starch, quebracho, tannin,dextrin and guar gum, and polyelectrolytes, such as polyphosphates andwater glass, which have a dispersant effect, often combined with adepressant effect. Other conventional additives that are known in theart of flotation are frothers (foaming agents), such as methyl isobutylcarbinol, triethoxy butane, pine oil, terpineol and polypropylene oxideand its alkyl ethers, among which methyl isobutyl carbinol, triethoxybutane, pine oil, terpineol, are preferred frothers. By way ofnon-limiting examples, preferred conventional additives are generallyfrothers, among which terpineol is the most commonly used.

Furthermore, one or more other conventional collector agents known inthe art of flotation, and preferably one or more conventional cationiccollector agents may be in the aqueous suspension formed in step c).Preferred conventional cationic collector agents are those containing nosulphur atoms, and most preferred are those containing only carbon,nitrogen and hydrogen atoms and optionally oxygen atoms. Conventionalcationic collector agents, in the form of their addition salts withacids, may however contain sulphur atom(s), when the salifying aciditself comprises sulphur atom(s), e.g. sulphuric, sulphonic or alkanesulphonic acid.

Examples of conventional cationic collector agents that may be presentin the suspension obtained from step c) may include, but are not limitedto fatty amines and their salts, as well as their alkoxylatedderivatives, fatty poly(alkylene amines) and their salts, e.g.polyethylene amines), poly(propylene amines) and their salts, as well astheir alkoxylated derivatives, fatty amidopolyamines, and their salts,as well as their alkoxylated derivatives, fattyamidopoly(alkyleneamines), and their salts, as well as their alkoxylatedderivatives, fatty imidazolines and their salts, as well as theiralkoxylated derivatives, N-fatty alkyl amino carboxylic acid and theirsalts, e.g. N-fatty alkyl amino propionic acid and their salts, alkylether amines and alkyl ether diamines and their salts, quaternaryammonium compounds, e.g. fatty quaternary ammonium compounds, mono(fattyalkyl) quaternary ammonium compounds, di(fatty alkyl) quaternaryammonium compounds, such as those described in WO 2007/122148 Al, andthe like.

A “polyamine” in the meaning of the present invention is a compoundcomprising two or more amine groups, the amine groups possibly beingsubstituted, i.e. the two or more amine groups may be identical ordifferent and be primary, secondary or tertiary amine groups.

Specific examples of conventional cationic collector agents that may bepresent in the suspension obtained from step c) may include, without anylimitation, dicoco-dimethyl ammonium chloride (CAS RN 61789-77-3),coco-dimethylbenzyl ammonium chloride (CAS RN 61789-71-7), tallowdimethylbenzyl ammonium chloride (CAS RN 61789-75-1), ethoxylated tallowmonoamine, 1,3-propanediamine-N-tallow diacetate (CAS RN 68911-78-4),N,N′,N′-tri-hydroxyethyl N-tallow propylene diamine (CAS RN 61790-85-0),N,N′,N′-tri-hydroxyethyl N-oleyl propylene diamine (CAS RN 103625-43-0),N,N′,N′-tri-hydroxyethyl N-lauryl propylene diamine (CAS RN 25725-44-4),fatty alkyl imidazoline obtained by condensation of diethylenetriamineand oleic fatty acid (CAS RN 162774-14-3), N,N′,N′-tri-hydroxyethylN-behenyl-propylene diamine (CAS RN 91001-82-0),isodecyloxypropyl-1,3-diaminopropane (CAS RN 72162-46-0), N,N-di(tallowcarboxyethyl)-N-hydroxyethyl-N-methyl ammonium methylsulphate (CAS RN91995-81-2), N-coco-β-aminopropionic acid (CAS RN 84812-94-2),N-lauryl-β-aminopropionic acid (CAS RN 1462-54-0),N-myristyl-β-aminopropionic acid (CAS RN 14960-08-8), their additionsalts with acid(s), sodium salt of N-lauryl-β-aminopropionic acid (CASRN 3546-96-1), triethanolamine salt of N-lauryl-β-aminopropionic acid(CAS RN 14171-00-7), triethanolamine salt of N-myristyl-β-aminopropionicacid (CAS RN 61791-98-8), as well as mixtures of two or more of theabove compounds, in all proportions, and the like.

“Etheramines” and “etherdiamines” in the meaning of the presentinvention are compounds comprising at least one ether group andrespectively a NH₂ terminal group and a NH₂ terminal group as well asanother primary, secondary or tertiary amine group.

If there are additives and/or conventional collector agents in thesuspension, the collector agent of the present invention may be presentfrom 1 wt.-% to 100 wt-%, more preferably from 10 wt.-% 100 wt.-%,typically from 20 wt.-% to 100 wt %, and advantageously from 1 wt.-% to99 wt.-%, more preferably from 10 wt.-% to 99 wt.-%, typically from 20wt-% to 99 wt.-% relative to the total amount of the collector agent andthe further additives.

Step D) of the Process of the Invention

Step d) of the process of the invention refers to passing a gas throughthe suspension formed in step c).

The gas may be generally introduced in the vessel of step d) via one ormore entry ports located in the lower half of the vessel. Alternativelyor additionally, the gas may be introduced via entry ports located on anagitation device in said vessel. The gas then naturally rises upwardsthrough the suspension.

Preferably the gas in the present invention may be air.

The gas may have a bubble size in the suspension of between 0.01 and 10mm, preferably of between 0.05 and 5 mm and most preferably between 0.1and 2 mm.

The gas flow rate in step d) may be adjusted, e.g. between 0.1 and 30dm³/min, preferably between 1 and 10 dm³/min and more preferably between3 and 7 dm³/min in a 4 dm³ flotation cell.

According to a preferred embodiment of the invention, step d) mayimplement an agitation cell and/or a flotation column and/or a pneumaticflotation device and/or a flotation device featuring a gas injection.

According to a preferred embodiment of the present invention, theaqueous suspension in step d) may have a temperature of between 5 and90° C., preferably between 10 and 70° C., more preferably of between 20and 50° C. and most preferably between 25 and 40° C.

Step d) may be preferably performed under agitation. Furthermore, stepd) may be continuous or discontinuous.

According to a preferred embodiment, step d) is performed until no morefoam is formed or can be visually observed or until no more impuritiescan be collected in the foam.

Step e) of the Process of The Invention

Step e) of the process of the invention refers to recovering the whitepigment containing product by removing the white pigment bearing phasefrom the aqueous suspension obtained after step d).

The inventive process comprises at least one indirect flotation step. Incontrast to conventional flotation, in which the desirable whitepigments are directly floated and collected from the produced froth,reverse or indirect flotation aims to have the undesirable impuritiespreferentially floated and removed, leaving behind a suspension that hasbeen concentrated in the desirable white pigments. According to thepresent invention, the inventive process leads to the formation of afroth containing the impurities and a white pigment bearing phase withthe white pigment containing product. The hydrophobised impurities aremigrating to the surface of the suspension and are concentrated in asupernatant foam or froth at the surface. This foam can be collected byskimming it off the surface, using for example a scraper, or simply byallowing an overflowing of the foam, and passing the foam into aseparate collection container. After collector the foam, the whitepigment bearing phase containing the non-floated white pigmentcontaining product will remain. The white pigment containing productremaining in the aqueous suspension can be collected by filtration toremove the aqueous phase, by decantation or by other means commonlyemployed in the art to separate liquids from solids.

The collected white pigment containing product can be subjected to oneor more further steps of froth flotation, according to the invention oraccording to prior art froth flotation methods.

According to a preferred embodiment, the white pigment bearing phaseobtained from step e) may be ground before and/or after step e).

The grinding step can be carried out with any conventional grindingdevice, for example by e.g. using a ball mill, a hammer mill, a rodmill, a vibrating mill, a roll crusher, a centrifugal impact mill, avertical bead mill, an attrition mill, a pin mill, a hammer mill.However, any other device that is able to grind the white pigmentcontaining product recovered during method step e) may be used.

Step e) of the inventive process may be followed by at least onegrinding or classification step for example by wet grinding andscreening to achieve a fine ground product slurry and/or at least oneother treatment step.

The hydrophobised impurities obtained by the inventive process and,preferably the hydrophobised silicates that are contained in the foamcan be collected as already set out above. In a preferred embodiment ofthe invention, the hydrophobised impurities may comprise silicates thathave a white colour as for example wollastonite, kaolin, kaoliniticclay, calcines kaolinitic clay, montmorillonite, talc, diatomaceousearth or sepiolite. More preferably, the hydrophobised impurity consistsof silicates that have a white colour and more preferably the impurityconsists of only one white coloured silicate. For example, the impuritymay consist only of wollastonite or kaolin or kaolinitic clay orcalcined kaolinitic clay or montmorillonite or talc or diatomaceousearth or sepiolite. These impurities obtained and separated from thewhite pigments according to the inventive flotation method may befurther processed and used in suitable applications. The impuritiescontaining only silicates having a white appearance when illuminated bydaylight and, preferably containing only one white silicate having awhite appearance when illuminated by daylight obtained by the inventiveprocess may be used in the same way than the white pigment containingproduct, for example in paper, plastics, paint, coatings, concrete,cement, cosmetic, water treatment, food, pharma, ink and/or agricultureapplications.

White Pigment Containing Product Obtained by the Process of theInvention

In a preferred embodiment the white pigment containing product obtainedby the process of the invention may comprise at least 95 wt.-% whitepigments, based on the dry weight, preferably at least 98 wt.-%, morepreferably at least 99 wt-% and most preferably at least 99.9 wt.-%,based on the dry weight.

In another embodiment the white pigment containing product obtained bythe process of the invention may comprise less than 60 ppm, preferablyless than 35 ppm, more preferably less than 15 ppm and most preferablyless than 5 ppm of collector agent or degradation products thereof basedon the dry weight.

The white pigment containing product as well as the white pigmentbearing phase obtained by the inventive process can be used in paper,plastics, paint, coatings, concrete, cement, cosmetic, water treatment,food, pharma, ink and/or agriculture applications. Preferably, the whitepigment containing product may be used in a wet end process of a papermachine, in cigarette paper, board, and/or coating applications, or as asupport for rotogravure and/or offset and/or ink jet printing and/orcontinuous ink jet printing and/or flexography and/or electrophotographyand/or decoration surfaces.

Where the term “comprising” is used in the present description andclaims, it does not exclude other elements. For the purposes of thepresent invention, the term “consisting of” is considered to be apreferred embodiment of the term “comprising of”. If hereinafter a groupis defined to comprise at least a certain number of embodiments, this isalso to be understood to disclose a group, which preferably consistsonly of these embodiments.

Where an indefinite or definite article is used when referring to asingular noun, e.g. “a”, “an” or “the”, this includes a plural of thatnoun unless something else is specifically stated.

Terms like “obtainable” or “definable” and “obtained” or “defined” areused interchangeably. This e.g. means that, unless the context clearlydictates otherwise, the term “obtained” does not mean to indicate thate.g. an embodiment must be obtained by e.g. the sequence of stepsfollowing the term “obtained” though such a limited understanding isalways included by the terms “obtained” or “defined” as a preferredembodiment.

The scope and interest of the invention will be better understood basedon the following examples which are intended to illustrate certainembodiments of the invention and are non-limitative.

In view of the above, some aspects of the invention relate to:

-   -   1. Process for manufacturing white pigment containing products,        characterised in that said process comprises the following        steps:        -   a) providing at least one white pigment and impurities            containing material;        -   b) providing at least one collector agent selected from the            group consisting of compounds of formula (1):

-   -   -   R¹ is selected from the group consisting of a direct bond,            an alkylene radical having from 1 to 10 carbon atoms, a            substituted alkylene radical, wherein said alkylene radical            is substituted by 1 or 2 —OH groups, a cycloalkylene group,            a cycloalkenylene group and an arylene group;        -   R² is selected from the group consisting of a hydrocarbyl            group having from 8 to 24 carbon atoms or a group of formula            R⁴—O-(A′O)_(w)-T-, wherein;            -   R⁴ represents a hydrocarbyl group having from 8 to 24                carbon atoms;            -   w is a number within the range from 0 to 20;            -   A′O is an alkyleneoxy group having from 2 to 4 carbon                atoms; and            -   T represents an alkylene group having from 1 to 6 carbon                atoms;        -   R³ is selected from the group consisting of a hydrocarbyl            group or a benzyl group;        -   AO represents an alkyleneoxy group having from 2 to 4 carbon            atoms;        -   X represents an anion derived from an alkylating agent R³X;        -   x is a number within the range from 1 to 20;        -   p is a number within the range from 1 to 15;        -   t is 0 or 1;        -   y is 0 or 1; and        -   G represents a group of formula (2);

-   -   -   wherein;        -   B represents an alkyl group having from 1 to 4 carbon atoms            or represents a benzyl group;        -   s is 1, 2 or 3;        -   R³, X and t are as defined above;        -   N⁺ is connected to R² in formula (1); and        -   (CH₂)_(s) is connected to the quaternary nitrogen atom in            formula (1);        -   c) mixing said white pigment and impurities containing            material of step a) and said collector agent of step b) in            an aqueous environment to form an aqueous suspension;        -   d) passing gas through the suspension formed in step c);        -   e) recovering the white pigment containing product by            removing the white pigment bearing phase from the aqueous            suspension obtained after step d).

    -   2. Process according to aspect 1, wherein the process involves        an indirect flotation step leading to the formation of a froth        containing the impurities and a white pigment bearing phase with        the white pigment containing product.

    -   3. Process according to any one of the preceding aspects,        wherein the white pigment is a white mineral pigment, preferably        selected from the group consisting of natural calcium carbonate        or ground calcium carbonate, calcium carbonate-comprising        mineral material, dolomite, barite, aluminium oxide, titanium        dioxide and mixtures of the foregoing.

    -   4. Process according to any one of the preceding aspects,        wherein the white mineral pigment is an alkaline earth metal        carbonate, preferably a calcium carbonate and most preferably        ground calcium carbonate.

    -   5. Process according to any one of the preceding aspects,        wherein the white pigment containing material comprises        impurities selected from the group consisting of iron sulphides,        iron oxides, graphite, silicates and mixtures thereof.

    -   6. Process according to aspect 5, wherein the silicate is        selected from the group consisting of quartz, a mica, an        amphibolite, a feldspar, a clay mineral and mixtures thereof and        preferably is quartz.

    -   7. Process according to aspect 5, wherein the silicate is a        white coloured silicate selected from the group consisting of        wollastonite, kaolin, kaolinitic clay, calcined kaolinitic clay,        montmorillonite, talc, diatomaceous earth, sepiolite and        mixtures thereof.

    -   8. Process according to any one of the preceding aspects,        wherein the amount of white pigment in the white pigment and        impurities containing material of step a) is from 0.1 to 99.9        wt.-%, based on the dry weight, preferably from 30 to 99.7        wt.-%, more preferably from 60 to 99.3 wt.-% and most preferably        from 80 to 99 wt.-%, based on the dry weight.

    -   9. Process according to any one of the preceding aspects,        wherein the ratio of white pigment:impurities in the white        pigment and impurities containing material of step a) is from        0.1:99.9 to 99.9:0.1, based on the dry weight, preferably from        30:70 to 99.7:0.3, more preferably from 60:40 to 99.3:0.7, and        most preferably from 80:20 to 99:1, based on the dry weight.

    -   10. Process according to any one of the preceding aspects,        wherein the white pigment and impurities containing material of        step a) has a weight median grain diameter in the range of from        1 to 1,000 μm, preferably of from 3 to 700 μm, more preferably        of from 5 to 500 μm and most preferably of from 10 to 80 μm or        from 100 to 400 μm.

    -   11. Process according to any of the preceding aspects, wherein        the compound of formula (1) is characterized as follows:        -   R¹ represents an alkylene radical having from 2 to 6 carbon            atoms, more preferably 4 carbon atoms;        -   R² represents a hydrocarbyl group containing from 12 to 24            carbon atoms or a group of formula R⁴—O-(A′O)_(w)-T-;            wherein            -   R⁴ represents a hydrocarbyl group having from 12 to 24                carbon atoms;            -   w is a number ranging from 0 to 10, preferably from 0 to                3;            -   A′O represents an alkyleneoxy group having from 2 to 4                carbon atoms; and            -   T represents an alkylene group having from 1 to 4 carbon                atoms, preferably having from 2 to 3 carbon atoms;        -   R³ represents an alkyl group having from 1 to 4 carbon            atoms;        -   X represents halogen, sulphate or carbonate;        -   AO represents an alkyleneoxy group having from 2 to 4 carbon            atoms, preferably having 2 carbon atoms;        -   x is a number within the range from 1 to 10; more preferably            within the range from 1 to 6; and        -   p is a number within the range from 1 to 10, preferably            within the range from 1 to 5.

    -   12. Process according to any one of the preceding aspects,        wherein the compound as provided in step b) is selected from the        group consisting of compounds of formula (1a)

-   -   -   wherein,        -   AO, p, t, x R¹, R², R³, and X are as defined in claim 1,            preferably as defined in aspect 11.

    -   13. Process according to aspect 12, wherein the compound of        formula (1a) is characterized as follows:        -   R¹ represents an alkylene radical having from 1 to 10 carbon            atoms, preferably having form 2 to 6 carbon atoms and more            preferably having 4 carbon atoms;        -   R² represents a hydrocarbyl group having from 8 to 24 carbon            atoms, preferably having from 12 to 24 carbon atoms;        -   R³ represents a hydrocarbyl group having from 1 to 4 carbon            atoms, preferably an alkyl group having 1 or 2 carbon atoms            and more preferably is a methyl group;        -   AO is an alkyleneoxy group, preferably an ethoxy group;        -   X is an anion derived from an alkylating agent R³X;            preferably chloride or sulphate;        -   x is a number within the range from 1 to 15, preferably            within the range from 2 to 10 and more preferably within the            range from 1 to 6;        -   p is a number within the range from 1 to 15; and        -   t is 0 or 1, preferably 1.

    -   14. Process according to aspect 12 or 13, wherein the compound        of formula (1a) possesses at least one of the following        characteristics:        -   R¹ is derived from a dicarboxylic acid, a dicarboxylic acid            chloride, a diester of a dicarboxylic acid, an anhydride of            a dicarboxylic acid, preferably R¹ is derived from a            compound selected from the group consisting of oxalic acid,            malonic acid, succinic acid, glutaric acid, adipic acid,            pimelic acid, phthalic acid, tetrahydrophthalic acid, malic            acid, tartaric acid, itaconic acid, the corresponding acid            chlorides, methyl or ethyl esters or anhydrides of these            compounds and mixtures thereof, preferably adipic acid;        -   R² is derived from a fatty amine selected from the group            consisting of 2-ethylhexylamine, 2-propylheptylamine,            n-octylamine, n-decylamine, n-dodecylamine, (coco            alkyl)-amine, (palm alkyl) amine, n-tetradecylamine,            n-hexadecylamine, n-octadecylamine, oleylamine, (tallow            alkyl)-amine, (hydrogenated tallow alkyl)-amine, (rape seed            alkyl)-amine, (soya alkyl)-amine, erucyl amine,            N-(n-decyl)-N-methyl-trimethylene-diamine,            N-(n-dodecyl)-N-methyl-trimethylene-diamine, N-(coco            alkyl)-N-methyl-trimethylene-diamine, N-(rape seed            alkyl)-N-methyl-trimethylene-diamine, N-(soya            alkyl)-N-methyl-trimethylene-diamine, N-(tallow            alkyl)-N-methyl-trimethylene-diamine, N-(hydrogenated tallow            alkyl)-N-methyl-trimethylene-diamine,            N-(erucyl)-N-methyl-trimethylene-diamine,            isotridecyloxypropylamine and mixtures thereof, preferably            (cow alley)-amine or (tallow alkyl)-amine;        -   R³ is derived from an alkylating agent selected from the            group consisting of dimethyl sulphate, diethyl sulphate,            dimethyl carbonate, benzyl chloride, methyl bromide, methyl            chloride, methyl iodide, preferably dimethyl sulphate or            methyl chloride and mixtures thereof.

    -   15. Process according to any one of the preceding aspects,        wherein, the collector agent of step b) consists of one or more        compounds of formula (1) or (1a).

    -   16. Process according to any one of the preceding aspects,        wherein the aqueous suspension obtained in step c) has a pH from        7 to 10, preferably from 7.5 to 9.5 and more preferably from 8.5        to 9.0.

    -   17. Process according to any one of the preceding aspects,        wherein the collecting agent is added in step c) in an amount of        from 1 to 5,000 ppm based on the total dry weight of the white        pigment and impurities containing material of step a),        preferably in an amount of from 20 to 2,000 ppm, more preferably        in an amount of from 30 to 1,000 ppm, and most preferably in an        amount of from 50 to 800 ppm based on the total dry weight of        said white pigment and impurities containing material of step        a).

    -   18. Process according to any one of the preceding aspects,        wherein the aqueous suspension obtained in step c) has a solids        content of between 5 and 80 wt.-% based on the total weight of        the solids in the suspension, preferably of between 10 and 70        wt.-%, more preferably of between 20 and 60 wt-% and most        preferably of between 25 and 55 wt.-% based on the total weight        of the solids in the suspension.

    -   19. Process according to any one of the preceding aspects,        wherein one or more additives are added to the aqueous        suspension prior to, during or after step c), wherein the        additives are selected from the group comprising pH-adjusting        agents, solvents, depressants, polyelectrolytes, frothers and        collector agents other than the collector agents according to        formula (1) and/or (1a).

    -   20. Process according to any one of the preceding aspects,        wherein the aqueous suspension obtained in step c) is ground        during and/or after step c).

    -   21. Process according to any one of the preceding aspects,        wherein the gas in step d) is air.

    -   22. Process according to any one of the preceding aspects,        wherein the suspension in step has a temperature of between 5        and 40° C., preferably between 10 and 40° C., more preferably        between 10 and 30° C. and most preferably between 15 and 25° C.

    -   23. Process according to any one of the preceding aspects,        wherein the white pigment bearing phase obtained from step e) is        dispersed and/or ground before and/or after step e) and        preferably is dispersed and/or ground in the presence of at        least one dispersing agent and/or at least one grinding aid        agent.

    -   24. Use of the white pigment bearing phase obtainable by the        process according to any of the preceding aspects in paper,        plastics, paint, coatings, concrete, cement, cosmetic, water        treatment, food, pharma, ink and/or agriculture applications,        wherein preferably the white pigment containing product is used        in a wet end process of a paper machine, in cigarette paper,        board, and/or coating applications, or as a support for        rotogravure and/or offset and/or ink jet printing and/or        continuous ink jet printing and/or flexography and/or        electrophotography and/or decoration surfaces.

EXAMPLES

1 Measurement Methods

pH Measurement

The pH was measured at 25° C. using a Mettler Toledo Seven Easy pH meterand a Mettler Toledo InLab® Expert Pro pH electrode. A three pointcalibration (according to the segment method) of the instrument wasfirst made using commercially available buffer solutions having pHvalues of 4, 7 and 10 at 20° C. (from Aldrich). The reported pH valueswere the endpoint values detected by the instrument (the endpoint waswhen the measured signal differs by less than 0.1 mV from the averageover the last 6 seconds).

Particle Size Distribution (Mass % Particles with A Diameter<X) andWeight Median Grain Diameter (d₅₀) of Particulate Material

The Particle Size Distribution (PSD) and the correlating median graindiameter d₅₀ were measured by Laser Diffraction Analyzers; either byMalvern Mastersizer 2000 in case of a d₅₀ above 5 μm or by aMicromeritics Sedigraph™ 5120 in case of finer materials (<5 μm). Themeasurement was carried out in an aqueous solution of 0.1% by weight ofNa₄P₂O₇ and the samples were dispersed using a high speed stirrer andultrasonic before. While in the Sedigraph works via the sedimentationmethod, i.e. an analysis of sedimentation behaviour in a gravimetricfield, the Mastersizer runs in a circulation mode.

Weight Solids (wt.-%) of a Material in Suspension

The weight solids were determined by dividing the weight of the solidmaterial by the total weight of the aqueous suspension. The weight ofthe solid material is determined by weighing the solid material obtainedby evaporating the aqueous phase of suspension and drying the obtainedmaterial to a constant weight.

Specific Surface (BET) Measurement

The specific surface area (in m²/g) of the white pigment or of theimpurities was determined using nitrogen and the BET method, which iswell known to the skilled man (ISO 9277:2010). The total surface area(in m²) of the white pigment or of the impurities was then obtained bymultiplication of the specific surface area and the mass (in g) of thewhite pigment or of the impurities. The method and the instrument areknown to the skilled person and are commonly used to determine specificsurface of white pigments or of the impurities.

Brightness Measurement and Yellow Index (=YI)

The samples from the flotation process were dried by use of microwave.The obtained dry powders were prepared in a powder press to get a flatsurface and Tappi brightness (R457 ISO brightness) is measured accordingto ISO 2469 using an ELREPHO 3000 from the company Datacolor. Theresults for the Tappi brightness are given as percentage in comparisonto a calibration standard.

The yellow index has been calculated by the following formula:YI=100*(R _(x) −R _(z))/R _(y))

Determination of the HCl Insoluble Content

10 g crude material (dry product or slurry under consideration of thesolid content) were weighted into a 400 ml beaker, suspended in 50 mldemineralized (demin.) water and mixed with 40 ml HCl (8N=25%). Afterthe formation of carbon dioxide has been finished the mixture was boiledfor 5 minutes, cooled to room temperature and subsequently strained overa previously weighed membrane filter. The beaker wall was rinsed 3 timeswith 20 ml demin. water and afterwards the filter was dried at 105° C.in the microwave until weight constancy is reached. After the filtercooled down in the desiccator it was weighed back and the HCl insoluble(insol.) content was calculated according to following equation:

${{HCl}\text{-}{{insol}.\mspace{14mu}{{content}\left\lbrack {\%\mspace{14mu}{by}\mspace{14mu}{weight}} \right\rbrack}}} = {\frac{{{filter}\mspace{14mu}{{gross}\lbrack g\rbrack}} - {{filter}\mspace{14mu}{{tare}\lbrack g\rbrack}}}{{weighed}\mspace{14mu}{{sample}\lbrack g\rbrack}\left( {{dry}\mspace{14mu}{mass}\mspace{14mu}{of}\mspace{14mu}{slurry}} \right)} \times 100\%}$

Determination of Load Capacity

The surface charge of the collector agent bearing particles in theslurry was measured by a Mūtek Particle Charge Detector (PCD04 from BTG)using titration with sodium polyethylenesulphonate (Na-PES) in [μVal/Kg].

Determination of the Acid Value

The acid value has been measured by potentiometric titration usingpotassium hydroxide solution as the reagent and isopropyl alcohol as asolvent. In a 250 mL beaker, about 10 g of sample to analyze isprecisely weighed (Sw, precision to the mg) and 70 mL of isopropylalcohol are added. The mixture has been agitated and heated gently ifnecessary to get a homogeneous sample. The titrator combined glassreference electrode has been introduced into the solution, which hasbeen then agitated with a magnetic stirrer. The acid-base titration ofthe sample has been performed using 0.1N aqueous potassium hydroxide(KOH) solution and the pH evolution has been recorded on the titrator.The equivalent point has been graphically determined using methods knownto the skilled in the art, and the volume (V_(KOH), in mL) of potassiumhydroxide solution used to reach this point has been determined. Theacid value (AV) has then been obtained according to the followingcalculation:

${AV} = \frac{\left\lbrack {{Normality}\mspace{14mu}{of}\mspace{14mu}{KOH}\mspace{14mu}{solution}\mspace{14mu}\left( {{mol}\text{/}L} \right)} \right\rbrack \times 56.1 \times V_{KOH}}{Sw}$

2 Collector Agents

Synthesis of Collector Agent 1 (CA1)

2,025.8 g ethoxylated coco alkyl amine (Noramox C5, supplied by CECA,France, contains 5 moles of ethoxy groups) and 0.2 g of hypophosphorousacid (50%) were introduced in a 4 litres round bottom flask. The mixturewas heated to 80° C. with nitrogen bubbling, afterwards the bubbling wasstopped and 503.7 g of adipic acid were added under agitation. After 15minutes the temperature of the mixture was raised to 160° C. during 1hour and the pressure in the vessel was lowered progressively until apressure of 6.67 kPa (50 mm Hg) was reached. After one hour at 160° C.and 6.67 kPa the mixture was heated to 200° C. and the mixture was keptat that temperature for 4 hours. Afterwards, the temperature was raisedto 220° C. and maintained until almost all acid is consumed (acidvalue<5 meq/g). The mixture was cooled down to 60° C. and the resultingesteramine (3) was recovered without any further treatment.

2,000 g of esteramine (3) were charged in a 6 litres glass reactor and300 g iso-propanol were added. Methyl chloride was added until thepressure in the glass reactor reached 2.9 bars, then the temperature wasraised to 85° C. and the mixture was kept between 80 to 85° C. untilcomplete reaction has occurred (complete reaction is achieved when thetotal amount of basic nitrogen is less or equal to 0.2 mmol·g⁻¹ asmeasured by titration with 0.2N hydrochloric acid in iso-propanol).Afterwards the mixture was allowed to cool down to 65° C. and thepressure was reduced to atmospheric pressure. After 2 hours of nitrogenbubbling through the mixture the obtained collector agent 1 (CA1) wasrecovered and diluted with iso-propanol to reach an iso-propanol-contentof 30 wt.-% as determined by proper gas chromatography analysis. Thecollector agent (CA1) is also known as polymer of adipic acid withethoxylated coco alkyl amine (also known as (coco alkyl)-amine) (5OE)which is totally quaternised with methyl chloride.

Synthesis of Collector Agent 2 (CA2)

2,201.7 g ethoxylated tallow alkyl amine (Noramox S5, supplied by CECA,France, contains 5 moles of ethoxy groups) and 0.2 g of hypophosphorousacid (50%) were introduced in a 4 litres round bottom flask. The mixturewas heated to 80° C. with nitrogen bubbling, afterwards the bubbling wasstopped and 503.7 g of adipic acid were added under agitation. After 15minutes the temperature of the mixture was raised to 160° C. during 1hour and the pressure in the vessel was lowered progressively until apressure of 6.67 kPa (50 mm Hg) was reached. After one hour at 160° C.and 6.67 kPa the mixture was heated to 200° C. and the mixture was keptat that temperature for 4 hours. Afterwards, the temperature was raisedto 220° C. and maintained until almost all acid is consumed (acidvalue<5 meq/g). The mixture was cooled down to 60° C. and the resultingesteramine (4) was recovered without any further treatment.

2,038.9 g of esteramine (4) were charged in a 6 litres glass reactor and305.8 g iso-propanol were added. Methyl chloride was added until thepressure in the glass reactor reaches 2.9 bars, then the temperature wasraised to 85° C. and the mixture was kept between 80 to 85° C. untilcomplete reaction has occurred (complete reaction is achieved when thetotal amount of basic nitrogen is less or equal to 0.2 mmol·g⁻¹ asmeasured by titration with 0.2N hydrochloric acid in iso-propanol).Afterwards the mixture was allowed to cool down to 65° C. and thepressure was reduced to atmospheric pressure. After 2 hours of nitrogenbubbling through the mixture the obtained collector agent 2 (CA2) wasrecovered and diluted with iso-propanol to reach an iso-propanol-contentof 30 wt.-% as determined by proper gas chromatography analysis. Thecollector agent (CA2) is also known as polymer of adipic acid withethoxylated tallow alkyl amine (also known as (tallow alkyl)-amine)(5OE) which is totally quaternised with methyl chloride.

Collector Agent 3 (CA3) (Comparative)

Reagent Lupromin FP 18 AS, polymeric esterquat, commercially availablefrom BASF.

Collector Agents 4 to 15 (CA4 to CA15)

The following other collector agents (CA4 to CA15) have been preparedfollowing the same reaction conditions as in example 1 and are obtainedby reacting the following compounds:

TABLE 1 Collector agents CA4 to CA15. Dicarboxylic Alkoxylated acid or aMolar Alkylating fatty amine derivative of ratio agent R³X for Collectorof formula formula (Ia) (II)/(Ia) or quaternisation agents (II) or (Ib)(II/Ib) reaction CA4 ethoxylated adipic acid 1.33 methyl chloride tallowalkyl amine (2OE) CA5 ethoxylated maleic acid 1.33 methyl chloridetallow alkyl amine (5OE) CA6 ethoxylated sebacic acid 1.33 methylchloride tallow alkyl amine (5OE) CA7 ethoxylated adipic acid 1.33methyl chloride oleylamine (5OE) CA8 ethoxylated adipic acid 1.33 methylchloride palm oil alkyl amine (5OE) CA9 ethoxylated adipic acid 1.33methyl chloride coco alkyl amine (2OE) CA10 ethoxylated succinic 1.33methyl chloride coco alkyl anhydride amine (5OE) CA11 ethoxylated adipicacid 1.5 methyl chloride tallow alkyl amine (2OE) CA12 ethoxylatedadipic acid 1.5 methyl chloride tallow alkyl amine (5OE) CA13ethoxylated adipic acid 1.33 dimethyl tallow alkyl sulphate amine (5OE)CA14 ethoxylated adipic acid 1.33 diethyl sulphate tallow alkyl amine(5OE) CA15 ethoxylated glutaric acid 1.33 methyl chloride tallow alkylamine (5OE)

In Table 1 the alkoxylated fatty amine of formula (II) are described bythe origin of the fatty alkyl chain. The number of ethylene oxide (OE)equivalents that have been reacted with the fatty alkyl amine are givenin brackets. All collector agents CA4 to CA15 are totally quaternised.

The collector agent CA4 to CA15 also shown good properties in theprocess for manufacturing white pigment containing products according tothe present invention.

3 Flotation Trials

All froth flotation trials were performed at room temperature (20±2° C.)in an Outotec laboratory flotation cell, equipped with a conical gassingagitator under agitation of 1,600 rpm under use of a 4 dm³ capacityglass cell. The solids content of the aqueous white pigment andimpurities containing material suspension added to the flotation machinewas of 33% by dry weight, said white pigment and impurities containingmaterial being sourced from sedimentary marble rock deposits withdifferent origins, running already a flotation process. The used waterwas original tab water from each local flotation process.

80%, a typical practiced dosage, of the flotation agent were given inthe beginning of the trial and mixed within a 2 min conditioning time. Asecond dosage was added depending on the achieved froth product andvisual seen impurities in the cell.

A flotation gas, consisting of air, was then introduced via orificessituated along the axis of the agitator at a rate of approximately 2dm³/min.

The foam created at the surface of the suspension was separated from thesuspension by overflow and skimming until no more foam could becollected, and both the remaining suspension and the collected foam weredewatered and dried in order to form two concentrates for mass balanceand quality analyses like carbon fraction determination.

Comparative Examples are marked with a “C” after the Example number.

Examples 1 to 3

For Examples 1 to 3 a white pigment and impurities containing materialfrom Gummern marble deposit in Austria is selected. The materialcontains 3.21 wt.-% of impurities determined by carbon fractiondetermination. The material is crushed and pre ground to a mediangrinding size d₅₀ of 20 μm. The material is treated according to theabove mentioned process. The test data are summarized in the following

Table 2.

TABLE 2 Flotation trials. White pigment Flotation data comprisingproduct Collec- Amount of Flotation Impu- Tappi- Test tor Collector timerities bright- Yellow- No. agent agent [ppm] [minutes] [wt.-%]^(a)) nessindex 1 CA1 300 15 0.79 91.18 2.44 2 CA1 400 20 0.05 93.40 2.43 3 CA1500 25 0.05 94.06 2.23 4 CA2 300 15 0.77 90.89 2.05 5 CA2 400 20 0.0693.06 2.52 6 CA2 500 25 0.05 93.73 2.39 7C CA3 400 20 0.95 90.70 1.94 8CCA3 500 20 0.08 93.58 2.22 9C CA3 600 25 0.06 93.90 2.09 ^(a))Impuritiesexpressed as compounds insoluble in 8N HCl.

As can be gathered from Examples 1 to 6 the inventive process formanufacturing white pigment comprising products shows good results (lowamount of impurities in the white pigment containing product, highvalues for Tappi-brightness and low values for yellow-indices) even atlow amounts of collector agent (test no. 2 or 3: 400 ppm) within theaqueous suspension. A process according to Comparative Examples 7C to 9Cuses collector agents according to the prior art and yields a productcomprising a higher amount of impurities. The comparison of the productspurified with the same amount of collector agents (test no. 2, 5 and 7C)shows that the products obtained by a process using collector agentsaccording to the invention have a lower amount of impurities.

4 Stability Tests

To investigate the stability of the reagent, it was stirred in parallelat 20° C. and at 40° C. for 24 h and the reduction of the positive Mytekcharge was controlled for defined time periods by using Na-PES asanionic titration agent. The resulting products were used afterwards forlab flotation tests in comparison to the original ones. The flotationtests were done at natural pH of 8.5 to 9.

TABLE 3 Stability tests. Temperature Time Load capacity Collector agent[° C.] [h:min] [μVal/kg] CA1 (inventive) 20 0 13 622 CA1 (inventive) 201:41 12 771 CA1 (inventive) 20 5:01 10 866 CA1(inventive) 20 23:30  10755 CA1(inventive) 40 0 13 622 CA1 (inventive) 40 1:12 13 361 CA1(inventive) 40 5:29 11 037 CA1(inventive) 40 22:55   9 799 CA3(comparative) 20 0 12 051 CA3 (comparative) 20 1:38 11 075 CA3(comparative) 20 4:58 90 53  CA3 (comparative) 20 23:30  61 63  CA3(comparative) 40 0 12 051 CA3 (comparative) 40 1:12  8 805 CA3(comparative) 40 5:29  6 320 CA3 (comparative) 40 22:52   5 101

The load capacity of the collector agent according to the inventionreduces by 21% at 20° C. and by 28% at 40° C. after approximately 24 h,whereas the collector agent according to the prior shows a reduction ofthe load capacity by 49% at 20° C. and 58% at 40° C. The results confirmthat the collector agents according to the invention show a higherstability in comparison to prior art collector agents.

Flotation trials according to the conditions as given in section 3 havebeen carried out with the original collector agents (test no. 10 and12C) and with collector agents which have been stored for 24 h at 40° C.as a 1 wt.-% aqueous solution (test no. 11 and 13C).

TABLE 4 Flotation trials. White pigment Flotation data comprising Amountof Flotation product Test Collector Collector time Impurities No. agentagent [ppm] [minutes] [wt.-%]^(a)) 10 CA1 500 25 0.05 11 CA1 500 25 0.0712C CA3 600 30 0.06 13C CA3 600 30 1.49 ^(a))Impurities expressed ascompounds insoluble in 8N HCl.

The results shown in Table 4 above confirm that the performance of thecollector agents according to the invention after and before storage ishigher than the performance of the prior art collector agents. Evenafter 24 h storage the performance of the collector agents according tothe invention is higher than the performance of the original prior artcollector agents (comparison of test no. 11 with test no. 12C).

The invention claimed is:
 1. A process for manufacturing white pigmentcontaining products, the process comprising the following steps: a)providing at least one white pigment and impurities containing material;b) providing at least one collector agent is selected from the groupconsisting of compounds of formula (1):

wherein R¹ is selected from the group consisting of i. a direct bond,ii. a C₁-C₂₀, linear or branched, saturated or unsaturated hydrocarbonchain optionally substituted by one or more —OH group(s), one or moremethyl and/or methylene groups, a cycloalkylene group, a cycloalkenylenegroup and/or an arylene group; R² is selected from the group consistingof a hydrocarbyl group having from 8 to 24 carbon atoms or a group offormula R⁴—O-(A′O)w-T- wherein, R⁴ represents a hydrocarbyl group havingfrom 8 to 24 carbon atoms; w is a number within the range from 0 to 20;A′O is an alkyleneoxy group having from 2 to 4 carbon atoms; and Trepresents an alkylene group having from 1 to 6 carbon atoms; R³ isselected from the group consisting of a hydrocarbyl group or a benzylgroup; AO represents an alkyleneoxy group having from 2 to 4 carbonatoms; X represents an anion derived from an alkylating agent R³X; x isa number within the range from 1 to 20; p is a number within the rangefrom 1 to 15; t is 0 or 1; y is 0 or 1; and G represents a group offormula (2);

wherein, B represents an alkyl group having from 1 to 4 carbon atoms orrepresents a benzyl group; s is 1, 2 or 3; R³, X and t are as definedabove; N⁺ in formula (2) is connected to R² in formula (1); and(CH₂)_(s) is connected to the quaternary nitrogen atom in formula (1);c) mixing the at least one white pigment and impurities containingmaterial of step a) and the at least one collector agent of step b) inan aqueous environment to form an aqueous suspension; d) passing gasthrough the suspension formed in step c) to separate the white pigmentfrom the impurities; and e) recovering the white pigment containingproduct by removing the white pigment from the aqueous suspensionobtained after step d).
 2. The process according to claim 1, wherein theprocess comprises performing an indirect flotation step that forms afroth containing the impurities and a white pigment bearing phase withthe white pigment containing product.
 3. The process according to claim1, wherein the white pigment is a white mineral pigment.
 4. The processaccording to claim 1, wherein the white mineral pigment is an alkalineearth metal carbonate.
 5. The process according to claim 1, wherein thewhite pigment containing material comprises impurities selected from thegroup consisting of iron sulphides, iron oxides, graphite, silicates andmixtures thereof.
 6. The process according to claim 5, wherein thesilicate is selected from the group consisting of a quartz, a mica, anamphibolite, a feldspar, a clay mineral and mixtures thereof.
 7. Theprocess according to claim 5, wherein the silicate is a white coloredsilicate selected from the group consisting of wollastonite, kaolin,kaolinitic clay, calcined kaolinitic clay, montmorillonite, talc,diatomaceous earth, sepiolite and mixtures thereof.
 8. The processaccording to claim 1, wherein the amount of white pigment in the whitepigment and impurities containing material of step a) is from 0.1 to99.9 wt.-%, based on the dry weight.
 9. The process according to claim1, wherein the ratio of white pigment:impurities in the white pigmentand impurities containing material of step a) is from 0.1:99.9 to99.9:0.1, based on the dry weight.
 10. The process according to claim 1,wherein the white pigment and impurities containing material of step a)has a weight median grain diameter in the range of from 1 μm to 1,000μm.
 11. The process according to claim 1, wherein in the compound offormula (1): R¹ represents an alkylene radical having from 2 to 6 carbonatoms; R² represents a hydrocarbyl group containing from 12 to 24 carbonatoms or a group of formula R⁴—O-(A′O)_(w)-T- wherein, R⁴ represents ahydrocarbyl group having from 12 to 24 carbon atoms; w is a numberranging from 0 to 10; A′O represents an alkyleneoxy group having from 2to 4 carbon atoms; and T represents an alkylene group having from 1 to 4carbon atoms; R³ represents an alkyl group having from 1 to 4 carbonatoms; X represents halogen, sulphate or carbonate; AO represents analkyleneoxy group having from 2 to 4 carbon atoms; x is a number withinthe range from 1 to 10; and p is a number within the range from 1 to 10.12. The process according to claim 1, wherein the compound as providedin step b) is selected from the group consisting of compounds of formula(1a)

wherein AO, p, t, x, R¹, R², R³, and X are as defined in claim
 1. 13.The process according to claim 12, wherein in the compound of formula(1a): R¹ represents an alkylene radical having from 1 to 20; R²represents a hydrocarbyl group having from 8 to 24 carbon atoms; R³represents a hydrocarbyl group having from 1 to 4 carbon atoms; AO is analkyleneoxy group having from 2 to 4 carbon atoms; X is an anion derivedfrom an alkylating agent R³X; x is a number within the range from 1 to15; p is a number within the range from 1 to 15; and t is 0 or
 1. 14.The process according to claim 12, wherein in the compound of formula(1a): R¹ is derived from a dicarboxylic acid, a dicarboxylic acidchloride, a diester of a dicarboxylic acid, an anhydride of adicarboxylic acid; and/or R² is derived from a fatty amine selected fromthe group consisting of 2-ethylhexylamine, 2-propylheptylamine,n-octylamine, n-decylamine, n-dodecylamine, (coco alkyl)-amine, (palmoil alkyl) amine, n-tetradecylamine, n-hexadecylamine, n-octadecylamine,oleylamine, (tallow alkyl)-amine, (hydrogenated tallow alkyl)-amine,(rape seed alkyl)-amine, (soya alkyl)-amine, erucyl amine,N-(n-decyl)-N-methyl-trimethylene-diamine,N-(n-dodecyl)-N-methyl-trimethylene-diamine, N-(cocoalkyl)-N-methyl-trimethylene-diamine, N-(rape seedalkyl)-N-methyl-trimethylene-diamine, N-(soyaalkyl)-N-methyl-trimethylene-diamine, N-(tallowalkyl)-N-methyl-trimethylene-diamine, N-(hydrogenated tallowalkyl)-N-methyl-trimethylene-diamine,N-(erucyl)-N-methyl-trimethylene-diamine, isotridecyloxypropylamine andmixtures thereof; and/or R³ is derived from an alkylating agent selectedfrom the group consisting of dimethyl sulphate, diethyl sulphate,dimethyl carbonate, benzyl chloride, methyl bromide, methyl chloride,methyl iodide, and mixtures thereof.
 15. The process according to claim12, wherein in the compound of formula (1a): R¹ is derived from acompound selected from the group consisting of adipic acid, maleicanhydride, sebacic acid and glutaric acid; R² is derived from aethoxylated fatty amine selected from the group consisting ofethoxylated (C₁₆-C₁₈) and C₁₈-unsaturated alkylamine, ethoxylated(C₈-C₁₆) and C₁₈-unsaturated alkylamine, ethoxylated (coco alkyl)-amine,ethoxylated oleylamine, ethoxylated (tallow alkyl)-amine and ethoxylated(palm oil alkyl)-amine; and R³ is derived from an alkylating agentselected from the group consisting of dimethyl sulphate, diethylsulphate and methyl chloride.
 16. The process according to claim 1,wherein, the at least one collector agent of step b) consists of one ormore compounds of formula (1).
 17. The process according to claim 1,wherein the aqueous suspension obtained in step c) has a pH from 7 to10.
 18. The process according to claim 1, wherein the at least onecollecting agent is added in step c) in an amount of from 1 ppm to 5,000ppm based on the total dry weight of the white pigment and impuritiescontaining material of step a).
 19. The process according to claim 1,wherein the aqueous suspension obtained in step c) has a solids contentof from 5 wt.-% to 80 wt.-% based on the total weight of the solids inthe suspension.
 20. The process according to claim 1, wherein one ormore additives are added to the aqueous suspension prior to, during orafter step c), wherein the additives are selected from the groupcomprising pH-adjusting agents, solvents, depressants, polyelectrolytes,frothers and collector agents other than the collector agents accordingto formula (1).
 21. The process according to claim 1, wherein theaqueous suspension obtained in step c) is ground during and/or afterstep c).
 22. The process according to claim 1, wherein the gas in stepd) is air.
 23. The process according to claim 1, wherein the suspensionin step c) has a temperature of from 5° C. and 40° C.
 24. The processaccording to claim 2, wherein the white pigment bearing phase obtainedfrom step e) is dispersed and/or ground before and/or after step e). 25.The process according to claim 1, wherein when R¹ is a C₁-C₂₀hydrocarbon, it is selected from the group consisting of a) an alkyleneradical having from 1 to 20 carbon atoms, and b) an alkenylene radicalhaving from 1 to 20 carbon atoms.
 26. The process according to claim 25,wherein when R¹ is the alkylene radical, it has from 1 to 10 carbonatoms.
 27. The process according to claim 25, wherein when R¹ is thealkylene radical, it is a substituted alkylene radical.
 28. The processaccording to claim 27, wherein the substituted alkylene radical issubstituted by 1 or 2 —OH groups, 1 or 2 methyl and/or methylene groups,a cycloalkylene group, a cycloalkenylene group and/or an arylene group.29. The process according to claim 25, wherein when R¹ is thealkenylene, the alkenylene has from 1 to 10 carbon atoms.
 30. Theprocess according to claim 25, wherein when R¹ the alkenylene radical,it is a substituted alkenylene.
 31. The process according to claim 30,wherein the substituted alkenylene radical is substituted by 1 or 2 —OHgroups, 1 or 2 methyl and/or methylene groups, a cycloalkylene group, acycloalkenylene group and/or an arylene group.
 32. The process accordingto claim 3, wherein the white mineral pigment is selected from the groupconsisting of natural calcium carbonate or ground calcium carbonate,calcium carbonate-comprising mineral material, dolomite, barite,aluminum oxide, titanium dioxide and mixtures of the foregoing.
 33. Theprocess according to claim 4, wherein the earth metal carbonate is acalcium carbonate.
 34. The process according to claim 33, wherein thecalcium carbonate is ground calcium carbonate.
 35. The process accordingto claim 6, wherein the silicate is a quartz.
 36. The process accordingto claim 8, wherein the amount of the white pigment in the amount of thewhite pigment and impurities containing material is from 30 to 99.7wt.-% based on dry weight.
 37. The process according to claim 8, whereinthe amount of the amount of the white pigment in the white pigment andimpurities containing material is from 60 to 99.3 wt.-% based on dryweight.
 38. The process according to claim 8, wherein the amount of theamount of the white pigment in the white pigment and impuritiescontaining material is from 80 to 99 wt.-% based on dry weight.
 39. Theprocess according to claim 9, wherein the ratio of whitepigment:impurities in the white pigment and impurities containingmaterial of step a) is from 30:70 to 99.7:0.3 based on dry weight. 40.The process according to claim 9, wherein the ratio of whitepigment:impurities in the white pigment and impurities containingmaterial of step a) is from 60:40 to 99.3:0.7 based on dry weight. 41.The process according to claim 9, wherein the ratio of whitepigment:impurities in the white pigment and impurities containingmaterial of step a) is from 80:20 to 99:1 based on dry weight.
 42. Theprocess according to claim 10, wherein the weight median grain diameteris from 3 μm to 700 μm.
 43. The process according to claim 10, whereinthe weight median grain diameter is from 5 μm to 500 μm.
 44. The processaccording to claim 10, wherein the weight median grain diameter is from10 μm to 80 μm.
 45. The process according to claim 10, wherein theweight median grain diameter is 100 μm to 400 μm.
 46. The processaccording to claim 11, wherein R¹ is an alkylene radical having 4 carbonatoms.
 47. The process of claim 11, wherein w in R⁴ is a number from 0to
 3. 48. The process according to claim 11, wherein T is an alkylenehaving from 2 to 3 carbon atoms.
 49. The process according to claim 11,wherein AO is an alkyleneoxy having 2 carbon atoms.
 50. The processaccording to claim 11, wherein x is a number within the range from 1 to6.
 51. The process according to claim 11, wherein p is a number withinthe range from 1 to
 5. 52. The process according to claim 13, wherein R¹is an alkylene radical having from 1 to 10 carbon atoms.
 53. The processaccording to claim 13, wherein R¹ is an alkylene radical, having form 2to 6 carbon atoms.
 54. The process according to claim 13, wherein R¹ isan alkylene radical having 4 carbon atoms.
 55. The process according toclaim 13, wherein R² is a hydrocarbyl group having from 12 to 24 carbonatoms.
 56. The process according to claim 13, wherein R³ is an alkylgroup having 1 or 2 carbon atoms.
 57. The process according to claim 13,wherein R³ is a methyl group.
 58. The process according to claim 13,wherein AO is an ethoxy group.
 59. The process according to claim 13,wherein X is chloride or sulphate.
 60. The process according to claim13, wherein x is a number within the range from 2 to
 10. 61. The processaccording to claim 13, wherein x is a number within the range from 1 to6.
 62. The process according to claim 13, wherein t is
 1. 63. Theprocess according to claim 14, wherein R¹ is derived from a compoundselected from the group consisting of oxalic acid, malonic acid,succinic acid, glutaric acid, glutaconic acid, adipic acid, muconicacid, pimelic acid, phthalic acid, terephthalic acid, tetrahydrophthalicacid, malic acid, maleic acid, fumaric acid, suberic acid, mesaconicacid, sebacic acid, azelaic acid, tartaric acid, itaconic acid, glutinicacid, citraconic acid, brassylic acid, dodecanedioic acid, traumaticacid, thapsic acid, the corresponding acid chlorides, methyl or ethylesters or anhydrides of these compounds and mixtures thereof.
 64. Theprocess according to claim 14, wherein R¹ is derived from a compoundselected from the group consisting of oxalic acid, malonic acid,succinic acid, glutaric acid, adipic acid, pimelic acid, phthalic acid,tetrahydrophthalic acid, malic acid, tartaric acid, the correspondingacid chlorides, methyl or ethyl esters or anhydrides of these compoundsand mixtures thereof.
 65. The process according to claim 14, wherein R¹is derived from adipic acid.
 66. The process according to claim 14,wherein R² is derived from a compound selected from the group consistingof (coco alky)-amine, (tallow alkyl)-amine and mixtures thereof.
 67. Theprocess according to claim 14, wherein R³ is derived from a compoundselected from the group consisting of dimethyl sulphate, methylchloride.
 68. The process according to claim 17, wherein the pH is from7.5 to 9.5.
 69. The process according to claim 17, wherein the pH isfrom 8.5 to 9.0.
 70. The process according to claim 18, wherein the atleast one collecting agent is added in step c) in an amount of from 20ppm to 2,000 ppm.
 71. The process according to claim 18, wherein the atleast one collecting agent is added in step c) in an amount of from 30ppm to 1,000 ppm.
 72. The process according to claim 18, wherein the atleast one collecting agent is added in step c) in an amount of from 50ppm to 800 ppm.
 73. The process according to claim 19, wherein thesolids content is from 10 wt.-% to 70 wt.-% based on the total weight ofthe solids in the suspension.
 74. The process according to claim 24,wherein the white pigment bearing phase is dispersed and/or ground inthe presence of at least one dispersing agent and/or at least onegrinding aid agent.
 75. The process according to claim 14, wherein R³ ismethyl chloride.
 76. The process according to claim 12, wherein, the atleast one collector agent of step b) consists of one or more compoundsof formula (1a).
 77. The process according to claim 12, wherein one ormore additives are added to the aqueous suspension prior to, during orafter step c), wherein the additives are selected from the groupcomprising pH-adjusting agents, solvents, depressants, polyelectrolytes,frothers and collector agents other than the collector agents accordingto formula (1a).